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\begin{document}

\title{Effect of early-life antibiotic exposure and IL-13 polymorphism on
atopic dermatitis phenotype}



\author[1]{Min Jee  Park}%
\author[1]{So-Yeon Lee}%
\author[2]{Si Hyeon  Lee}%
\author[3]{Mi-Jin Kang}%
\author[1]{Kun Baek Song}%
\author[4]{Sungsu  Jung}%
\author[5]{Ji-Sun  Yoon}%
\author[6]{Dong In Suh}%
\author[7]{Youn Ho Shin}%
\author[8]{Kyung Won Kim}%
\author[9]{Kangmo Ahn}%
\author[1]{Soo-Jong Hong}%
\affil[1]{Asan Medical Center}%
\affil[2]{University of Ulsan College of Medicine}%
\affil[3]{Asan Institute for Life Sciences}%
\affil[4]{Yangsan Busan Daehakgyo Byeongwon}%
\affil[5]{MediplexSejong Hospital}%
\affil[6]{Seoul National University Children's Hospital}%
\affil[7]{CHA Gangnam Medical Center}%
\affil[8]{Yonsei University College of Medicine}%
\affil[9]{Sungkyunkwan University School of Medicine at Samsung Medical Center Cancer Center}%


\vspace{-1em}



  
  \date{May 18, 2024}


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\selectlanguage{english}
\begin{abstract}
Background: Although atopic dermatitis (AD) is associated with certain
gene variants, the rapidly increasing incidence of AD suggests that
environmental factors contribute to disease development. In this study,
we investigated the association of AD incidence and phenotype with
antibiotic exposure within 6 months of age, considering the dose
administered and genetic risk. Methods: This study included 1,637
children from the COCOA birth cohort. Pediatric allergists assessed the
presence of AD at each visit and obtained information about antibiotic
exposure for more than 3 days. IL-13 (rs20541) polymorphism was
genotyped by the TaqMan method. We stratified the AD phenotypes into 4
groups and used multinomial logistic regression models for analysis.
Results: Antibiotic exposure within 6 months of age was found to
increase the risk of AD within 3 years of life (aOR=1.40, 95\%, CI
1.09--1.81) in dose-dependent manner. Antibiotic exposure more than
twice increased the risk of the early-persistent AD phenotype (aOR=2.50,
95\% CI 1.35--4.63). There was a weak interaction between genetic
polymorphisms and environmental factors on the development of AD (p for
interaction=0.06). Children with the IL-13 (rs20541) GA+ AA genotype
have a higher risk of the early-persistent AD phenotype when exposed to
antibiotics more than twice than those with the IL-13 (rs20541) GG
genotype and without exposure to antibiotics (aOR=4.73, 2.01--11.14).
Conclusion: Antibiotic exposure within 6 months was related to the
incidence of early-persistent AD and a dose-dependent increase in the
incidence of AD in childhood, whose effect was modified by the IL-13
(rs20541) genotype.%
\end{abstract}%



\sloppy


\textbf{Authorship:} Park, Min Jee: Formal analysis (Lead);
Writing-original draft (Lead). Lee, So-Yeon: Conceptualization (Lead);
Writing-review \& editing (Equal). Lee, Si Hyeon: Software (Lead). Kang,
Mi-Jin: Methodology (Lead). Song, Kun Baek: Data curation (Supporting);
Validation (Equal). Jung, Sungsu: Investigation (Supporting); Resources
(Supporting). Yoon, Ji-Sun: Data curation (Supporting); Resources
(Supporting). Suh, Dong In: Project administration (Equal); Resources
(Equal). Shin, Youn Ho: Project administration (Equal); Resources
(Equal). Kim, Kyung Won: Project administration (Equal); Resources
(Equal). Ahn, Kangmo: Project administration (Equal); Resources (Equal).
Hong, Soo-Jong: Conceptualization (Lead); Project administration
(Equal); Writing-review \& editing (Lead).

\textbf{Key message:} Being wary of unwarranted prescription of
antibiotics, especially in vulnerable children, might be helpful in
preventing AD development in infants and modification of its clinical
course.

\textbf{Conflicts of interest}

The authors declare no conflicts of interest in relation to this study.

\textbf{Financial support}

Min Jee Park, So-Yeon Lee, Eun-Sang Rhee, Si Hyeon Lee, Mi-Jin Kang, Kun
Baek Song, Sungsu Jung, Jisun Yoon, Dong In Suh, Youn Ho Shin, Kyung Won
Kim, Kangmo Ahn, and Soo-Jong Hong have the following content of
financial relationships.

This research was supported by the Research Program funded by the Korea
Disease Control and Prevention Agency (2008-E33030-00, 2009-E33033-00,
2011-E33021-00, 2012-E33012-00, 2013-E51003-00, 2014-E51004-00,
2014-E51004-01, 2014-E51004-02, 2017-E67002-00, 2017-E67002-01,
2017-E67002-02); and Bio \& Medical Technology Development Program of
the National Research Foundation (NRF) funded by the Korean government
(MSIT) (2017M3A9F3043834)

The funders had no role in the study design, data collection and
analysis, decision to publish, or preparation of the manuscript.

\textbf{Ethical approval}

The study was approved by the Institutional Review Boards of Asan
Medical Center (IRB No. 2008-0616), the Samsung Medical Center (IRB No.
2009-02-021), the Severance Hospital (IRB No. 4-2008-0588), and the CHA
Medical Center (IRB No. 2010-010). Written informed consent was obtained
from each mother and her husband before the study-related interview was
conducted. The obtainment of consent was confirmed by the IRB.

\textbf{Abstract}

\textbf{Background:} Although atopic dermatitis (AD) is associated with
certain gene variants, the rapidly increasing incidence of AD suggests
that environmental factors contribute to disease development. In this
study, we investigated the association of AD incidence and phenotype
with antibiotic exposure within 6 months of age, considering the dose
administered and genetic risk.

\textbf{Methods:} This study included 1,637 children from the COCOA
birth cohort. Pediatric allergists assessed the presence of AD at each
visit and obtained information about antibiotic exposure for more than 3
days. \emph{IL-13} (rs20541) polymorphism was genotyped by the TaqMan
method. We stratified the AD phenotypes into 4 groups and used
multinomial logistic regression models for analysis.

\textbf{Results:} Antibiotic exposure within 6 months of age was found
to increase the risk of AD within 3 years of life (aOR=1.40, 95\%, CI
1.09--1.81) in dose-dependent manner. Antibiotic exposure more than
twice increased the risk of the early-persistent AD phenotype (aOR=2.50,
95\% CI 1.35--4.63). There was a weak interaction between genetic
polymorphisms and environmental factors on the development of AD (p for
interaction=0.06). Children with the \emph{IL-13 (rs20541)} GA+ AA
genotype have a higher risk of the early-persistent AD phenotype when
exposed to antibiotics more than twice than those with the \emph{IL-13
(rs20541)} GG genotype and without exposure to antibiotics (aOR=4.73,
2.01--11.14).

\textbf{Conclusion:} Antibiotic exposure within 6 months was related to
the incidence of early-persistent AD and a dose-dependent increase in
the incidence of AD in childhood, whose effect was modified by
the\emph{IL-13} (rs20541) genotype.

\textbf{Key words:} dermatitis, atopic; phenotype; anti-bacterial
agents; \emph{IL-13} ; polymorphism

\textbf{Introduction}

Atopic dermatitis (AD) is a chronic, recurrent inflammatory skin disease
characterized by itching eczematous lesions, and it is the leading cause
of health burden due to non-fatal skin-related disease globally.(1) The
prevalence rate of childhood AD ranges from 15\% to 20\%(2) and varies
widely from one country to another globally. In Korea, primary surveys
of children and adolescents demonstrated increasing trends in the
prevalence of AD symptoms within the last 12 months.(3)

To identify the cause of AD and to effectively prevent and manage it,
many epidemiological studies have been conducted on hygiene hypothesis.
This hypothesis states that the Western lifestyle not only limits
infection and microbial exposure but also alters the colonization of the
gut microbiome, thereby disrupting the development of the immune system
and leading to allergic disease. As part of this concept, there is
growing evidence that the increased prevalence of allergic diseases can
be attributed to increased exposure to antibiotics.(4) In particular,
the antibiotic prescription rate for all pediatric patients increased
from 34.8\% in 2010 to 70.4\% in 2014 in Korea.(5) Therefore, it is
necessary to investigate the relationship between increasing exposure to
antibiotics and the development of AD. Previous studies have
demonstrated that the composition and function of the gut microbiome at
6 months of age could affect the course of AD in early childhood (6) and
antibiotic administration aggravates clinical signs in a mouse model of
AD (7). No other studies have analyzed the severity and natural course
of AD according to the frequency of early-life antibiotic exposure.
Thus, considering these factors, we hypothesized that antibiotic
exposure within the first 6 months of life affects not only the severity
of AD but also the natural course of AD through changes in the
microbiome. In this prospective birth cohort study, we focused on the
relationship between the development of AD and antibiotic exposure
within 6 months, a critical period in the development of the microbiome
and the immune system, and further examined whether the frequency of
antibiotic exposure is differently associated with the severity and
phenotypes of AD.

AD was considered a TH\textsubscript{2} disease characterized by
interleukin (IL)-4 and 13 signaling. \emph{IL-13} has a significant
impact on the alteration of the skin microbiome, causing the
deterioration in barrier function of the skin, and it may be a more
important mediator for the TH\textsubscript{2} response in the skin
than\emph{IL-4.} (8) Previous studies have identified that polymorphisms
in the \emph{IL-13} promoters are associated with the development of
AD,(9, 10) and among them, many studies have focused on rs20541,
especially in terms of its relationship with AD, in the existing Asian
population.(11-13) Following on from the above considerations, we
hypothesized that antibiotic exposure influences the AD phenotype and
this relationship can be modified by \emph{IL-13} polymorphism. In this
study, we explored the association of the occurrence and phenotype of AD
with antibiotic exposure within 6 months of age, considering the dose
administered and \emph{IL-13} (rs20541) polymorphism.



\textbf{Methods}

\textbf{Study population}

The COCOA (COhort for Childhood Origin of Asthma and Allergic diseases)
comprised the general Korean population and aimed to investigate the
causal contribution of genetics, perinatal environment, maternal
lifestyle, and psychosocial stress of the mother and child on pediatric
susceptibility to allergic diseases.(14) (See ``study population'' in
the Online Repository)

Of the 2,846 enrolled infants, 488 were lost to follow-up; children with
incomplete questionnaire data about AD and antibiotic exposure until 5
years of age were excluded. The remaining 1,637 children were included
in this study.

\textbf{DNA Collection and SNP Genotyping}

Genomic DNA was extracted from the cord blood mononuclear cells of each
child and genotyped for \emph{IL-13} (rs20541) polymorphisms using the
TagMan assay (ABI, Foster City, CA, USA). The endpoint fluorescent
readings were measured on an ABI 7900HT Sequence Detection System (ABI,
Foster City, CA, USA). The details of the methods are described in a
previous study.(15) Duplicate samples and negative controls were
included to ensure genotyping accuracy.

\textbf{Physician's assessment of allergic diseases and antibiotic
exposure}

The presence of AD was clinically diagnosed by pediatric allergists on
the basis of the Hanifin and Rajka criteria.(16) Presence of AD was
defined as physician-diagnosed AD in the preceding 12 months during each
follow-up annually, and the incidence of AD was defined as the number of
new cases of physician-diagnosed AD that developed since birth over a
defined period. At consecutive visits, AD patients were assessed by
pediatric allergists using the SCORing Atopic Dermatitis (SCORAD).
Higher numbers indicate greater severity, and the scale ranges from 0 to
103.(17) AD severity was categorized as mild (\textless{}15) and
moderate to severe ([?]15) according to the objective components of the
index (clinical signs and disease extent).(18)

Early antibiotic treatment was defined as exposure to antibiotics for
more than 3 days within the first 6 months of life, regardless of
whether the infant was hospitalized or not, and pediatric allergists
obtained the information about the antibiotics at each visit after
birth.

\textbf{Outcomes}

Our primary outcome of interest was AD incidence at the age of 6 months
and 1 to 3 years according to the frequency of antibiotic exposure
within 6 months as assessed by pediatric allergists. Other primary
outcomes were the influence of antibiotic exposure on AD phenotypes and
investigator-reported clinical signs (SCORAD).

The secondary outcomes were AD incidence at the age of 6 months and 1 to
3 years according to IL-13 genetic variations. Other secondary outcomes
were combined effects of IL-13 genetic variations and antibiotic
exposure on the AD incidence and phenotypes. Two transition periods were
considered, namely, age from 6 months to 2 years and from 2 to 5 years,
to classify AD phenotypes. We defined four different phenotypes of AD:
the early-transient phenotype, with AD onset within 2-years of age and
no further symptoms later; the early-persistent phenotype, with onset
within 2 years of age and symptoms do not improve within less than 2
years; the late phenotype, with onset after 2 years of age; and the
non-AD.(19)

\textbf{Statistical analysis}

Data are presented as frequencies and proportions for categorical
variables. Chi-square test and Fisher's exact test were performed to
evaluate the associations between the incidence of AD at the age of 1
year and the variables. To assess effect modification according
to\emph{IL-13} polymorphisms and early-life antibiotic exposure,
subjects were divided into 4 groups according to environmental factors
(antibiotic use within 6 months for more than 3 days) and genetic
background (genotypes) and multivariable logistic regression models were
performed with the data to estimate adjusted odd ratios (aOR) and the
corresponding 95\% confidence intervals (95\% CI) for a comparison of AD
occurrence risk by relevant covariates after adjusting for potential
confounders: sex, maternal education level, family history of allergic
diseases, history of breastfeeding, and mode of delivery. Multinomial
logistic regression analysis was also used to identify the effects of
the use of antibiotics within 6 months of age and the combined effect of
the use of antibiotics and IL-13 genetic variations on AD phenotypes.
Finally, we tested for trends regarding the effect of the risk factors
(early-life environmental factors and genetic polymorphisms) on the
development of AD by two-factor analysis of variance (two-way ANOVA).
All statistical tests were two-sided, and significance levels of p
values were set at \textless{}0.05. Statistical analyses were performed
using SPSS Statistics, version 23.0 (IBM SPSS Statistics, Inc., Chicago,
IL).



\textbf{Results}

\textbf{Study population}

The demographic characteristics of the participants are shown in Table
1. Children diagnosed with AD at 1 year accounted for 25.3\% of the
study subjects, with a higher proportion of boys, when compared to
non-AD children. No significant differences were observed in the
prevalence of antibiotic exposure during pregnancy and history of acute
bronchiolitis within 6 months (p=0.85 and 0.17, respectively).

\textbf{Association between antibiotic exposure within 6 months of age
and AD}

In multivariable regression analyses, antibiotic exposure within 6
months of age increased the risk of AD at each visit after adjusting for
sex, maternal education, family history of allergic disease,
breastfeeding, and mode of delivery (Fig. 1; at the age of 6 months:
aOR=1.30, 95\% CI 0.99--1.71, p=0.06; at 1 year: aOR=1.28, 95\% CI
1.00--1.65, p=0.05 at 2 years: aOR=1.38, 95\% CI 1.08--1.77, p=0.01; at
3 years: aOR=1.40, 95\% CI 1.09--1.81, p=0.01). Furthermore, the more
the antibiotics were prescribed, the higher was the dose-dependent risk
of AD at 6 months to 3 years (Fig. E1).

\textbf{Association between antibiotic exposure within 6 months of age
and AD phenotypes}

We define 4 different phenotypes of AD(19): the early-transient
phenotype (n = 111; 14.8\%), the early-persistent phenotype (n = 199;
26.5\%), the late phenotype (n = 70; 14.8\%), and the never/infrequent
phenotype (n = 370; 49.3\%).

Antibiotic exposure within 6 months of life was associated with
early-persistent AD compared with non-AD (Table 2; aOR=1.84, 95\% CI
1.18--2.86), and the odds increased with a greater number of antibiotic
treatment courses (once: aOR=1.51, 95\% CI 0.90--2.55; [?]2 times:
aOR=2.50, 95\% CI 1.35--4.63; p=0.049). There was no relationship
between antibiotic exposure and phenotypes other than early-persistent
AD.

\textbf{Association between antibiotic exposure within 6 months of age
and severity of AD}

According to the SCORAD index, when antibiotic exposure occurred within
6 months of age, 55 patients (66.3\%) had mild AD and 28 patients
(33.7\%) had moderate to severe AD at the age of 1 year. In contrast,
when antibiotic exposure did not occur, the severity of AD at 1 year was
predominantly mild, accounting for 82.5\% of the cases (Table 3,
p\textless{}0.01). Mean SCORAD score was 9.42 (SD = 10.00) in 1 year
children with AD who were exposed to antibiotics, which was
significantly higher than that of AD patients who did not have exposure
to antibiotics within the first 6 months of life (p=0.02).

\textbf{Combined effects of \emph{IL-13} gene polymorphism} \textbf{and
antibiotic exposure within 6 months of age on AD development}

We found some evidence for the interaction between genetic polymorphisms
and environmental factors on the development of AD (p for
interaction=0.06). Compared to infants who were not exposed to
antibiotics within the first 6 months of age and had the
\emph{IL-13}(rs20541) GG genotype, those who were exposed to antibiotics
and had the\emph{IL-13} (rs20541) GA+AA genotype had a higher risk of AD
at a young age (Table 4).

Regarding antibiotics, the dose--response relationship was particularly
notable in children with \emph{IL-13} (rs20541) GA+AA genotype (Fig.
E2). The higher the number of prescriptions, the higher was the risk of
AD at 2- and 3-year-old children (at 2 years, once: aOR=1.49, 95\% CI
0.96--2.32; [?]2 times: aOR=2.00, 95\% CI 1.18--3.42; at 3 years, once:
aOR=1.57, 95\% CI 1.00--2.46; [?]2 times: aOR=1.96, 95\% CI 1.13--3.38)

\textbf{Association between antibiotic exposure within 6 months of age
and \emph{IL-13} gene polymorphism on the phenotypes of AD}

In the final model, we considered the combined effects of
\emph{IL-13}gene polymorphism and antibiotic exposure within the first 6
months of age on the phenotypes of AD. The\emph{IL-13} (rs20541) GA+AA
genotype was associated with early-persistent AD when the non-AD with GG
genotype was considered as a reference (Table 5). Of children with the
\emph{IL-13} (rs20541) GA+AA genotype, children who were exposed with
antibiotics more than 2 times was associated with a higher risk of
early-persistent AD than those who were exposed with antibiotics only
once, and this effect was even pronounced in infants who were never
exposed with antibiotics (never: aOR=2.06, 95\% CI 1.13-3.77; once:
aOR=2.99, 95\% CI 1.44--6.22; [?]2 times: aOR=4.73, 95\% CI 2.01--11.14).



\textbf{Discussion}

This prospective birth cohort study revealed that most children who were
at risk of developing AD, especially the early-persistent AD phenotype,
had antibiotic exposure within 6 months of life, which occurred in a
dose-dependent manner. Moreover, the relationship between antibiotic
exposure and the development and persistency of AD can be modified
by\emph{IL-13} genetic susceptibility. These findings suggest that early
life antibiotic exposure to a certain extent contributes to the
development of AD and phenotype, especially in susceptible infants, and
this can be modified by efforts toward primary prevention.

Despite antibiotic exposure in early life being a plausible risk factor
for the development of AD in children, existing epidemiological evidence
is controversial. Our finding on the association of antibiotics with AD
in dose-response manner was similar to those in previous reports. A
systematic review reported a significant positive dose--response
association and approximately 7\% increase in the risk of AD due to
antibiotic exposure during the first year of life.(20) Another
prospective cohort study from Japan reported that an increase in the
current AD risk in 5-year-old children is due to antibiotic exposure
within the first 2 years of life.(21) However other studies concluded
that there was no such relationship between antibiotic exposure in
infancy and the development of AD.(22, 23) Differences in results could
be due to differences in exposure to antibiotic dose, types of
antibiotics, exposure time, definition and timing of outcome, and target
sample size.

Although the basic etiology of AD is not fully known, it is thought to
be attributable to complex, but interrelated biologic pathways, such as
dysfunction of the skin barrier and altered innate or adaptive immune
responses.(24) The recent increase in the incidence of AD seems to be
due to changes in lifestyles and environmental factors. For example,
there is evidence that increasing antibiotic exposure in early life
contributes to increased AD susceptibility in children. Note that the
exposure to at least one antibiotic between 0-6 months and 0-1 year
occurred in 34.3\% and 67.4\% of the study population, which comprised
the COCOA study population (data not shown); this rate was higher than
those reported in other studies.(21, 25) Therefore, much attention
should be paid to various antibiotic exposure-related factors
influencing human health.

The hypothesized mechanism was supported by findings of studies showing
antibiotic-induced killing of commensal bacteria is important for the
normal development of immune function, which in turn, leads to gut
dysbiosis of the microbial community in infants. This increases the risk
of developing allergic conditions later in life. In mouse model studies,
antibiotics administration exacerbated clinical signs of AD and caused
gut dysbiosis such as increased levels of Th2 cytokine \emph{IL-4} with
significantly suppressed short-chain fatty acid levels, which influence
Treg cell induction and enhance barrier function.(7) To identify
potentially relevant gut microbiome changes in the early life with
regard to antibiotics use and AD outcomes in children, we additionally
analyzed the fecal samples of 235 Korean infants who were enrolled in
COCOA study (See ``\textbf{Gut microbiome analysis} '' in the Online
Repository). The relative abundance of Firmicutes was significantly
lower and Fusobacteria composition was significantly higher in AD
subjects with antibiotic exposure compared with those without antibiotic
exposure (Fig. E3A, E3B), which is consistent with other studies.(26,
27) Recent evidence indicates that a disproportionate
representation-such as a decrease or increase in the composition-of
Firmicutes and Fusobacteria can impact the CD4 T cell function and
development of immune pathology in intestine.(26, 27) Therefore,
antibiotic exposure in early life may affect immune development through
changes in gut microbiomes, which attribute to increase the incidence of
AD.

Another pathogenetic mechanism is that gut epithelial barrier
destruction through the disturbance of microbiota after antibiotic
administration may lead to tissue damage and allergic sensitization.(28)
The aforementioned studies suggest that gut epithelial inflammation
resulting from antibiotic-induced dysbiosis may play a decisive role in
the development, persistence, or aggravation of AD.

Several studies have indicated that \emph{IL-13 (rs20541)} is associated
with the risk of AD(9, 29) and there may be gene--environment
interactions between \emph{IL-13} polymorphisms and antibiotic exposure
in early life, which affects the clinical features of allergic
diseases.(11) Since studies regarding the association of AD phenotypes
with these factors are lacking, this study focused on the effect of the
interaction between risk genes and environmental risk factors and
demonstrated that while antibiotic exposure in early life itself may
influence the development of AD, especially early-persistent AD, this
trend was particularly notable in infants carrying the \emph{IL-13
(rs20541)} variant. However, we should note that we had limited power to
detect such an interaction.

Key factors of AD are defects in the skin barrier function, abnormality
of the skin immunologic barrier, and dysbiosis, which may aggravate each
other. Gut dysbiosis induced by antibiotics was associated with
reduction in mucosal CD4+T cells expressing IFN-\selectlanguage{greek}γ \selectlanguage{english}which play a role in
maintaining the barrier function of the skin,(27) therefore predisposes
the infants to cutaneous disease. In addition, when considering the
complex nature of AD along with genetic and environmental risk
factors,\emph{IL-13} genetic polymorphism increases \emph{IL-13}
production, which affects the expression level of the skin barrier
protein,(13) and this may have an additional role in aggravating the
barrier function of the skin. Further studies regarding skin barrier
disturbance, microbiome and metabolite\textbackslash{}souts induced
during early life antibiotic exposure are needed to support a plausible
biological pathway.

The strength of our study is the use of a large general population-based
birth cohort and the measurement of potential confounders included in
the analysis. We found the results for AD to be similar to those in
previous studies, suggesting that antibiotic exposure in early life was
associated with the risk of childhood AD.(30, 31) Our study is also
strengthened by the use of pediatric allergist's medical report of
doctor-diagnosed AD as the outcome variable. In addition, this study
assessed the effects of antibiotic exposure in the first 6 months of
life, focusing on not only the occurrence but also the severity and
persistency of AD in childhood, raising awareness about the prescription
of antibiotics that can be abuse.

This study also had some limitations. First, our cohort study could not
determine the exact dose, total duration, and types of antibiotics that
could influence the effect of antibiotics on immune responses. As
broad-spectrum antibiotics were found to have stronger effects than the
narrow-spectrum one,(23) further study by utilization of the National
Health Insurance data is needed to confirm these specific effects of
individual antibiotics on AD. Another limitation is the increased
incidence of skin infections in children with AD, which makes it
difficult to identify a genuine causal association, as children are more
likely to receive antibiotics. Additional studies are needed to confirm
the causality and prove the mechanism by which antibiotic exposure at a
young age causes changes in the skin or gut microbiome and leads to the
development of AD. Moreover, acute bronchiolitis, one of the main causes
of antibiotic exposure in early life, is a long-term risk factor for
asthma; hence, frequent bronchiolitis may be related to predisposition
to allergy. However, there was no significant difference in the history
of acute bronchiolitis within the first 6 months of life according to
the diagnosis of AD. More studies are still needed on maternal
antibiotic administration during pregnancy, antibiotic exposure after 6
months after birth, and confounding factors caused by maternal and child
infections.

Although AD is not a life-threatening disease, more than 60\% of
children with AD are predisposed to develop one or more atopic
comorbidities, such as food allergy, asthma, or allergic rhinitis, which
is so-called ``atopic march.''(32) Therefore, it is important to define
the exact role of early-life antibiotic exposure to evaluate its
association with the development and clinical course of AD and
progression to other allergic diseases to make successful strategies in
allergy prevention. Our present study suggested that children with
antibiotic exposure early in life were at risk of developing
early-persistent AD, and a dose--response relationship was observed in
young children, particularly in infants carrying \emph{IL-13} (rs20541)
genetic susceptibility alleles. Attention needs to be paid to
unwarranted prescription of antibiotics, especially in susceptible
children receiving primary care. This study will improve our
understanding on the influence of genetic and environmental causes and
their interactions on childhood AD and provide comprehensive insights
into the pathogenesis and phenotype of AD and therefore enable improved
prevention.

\textbf{References}

1 Weidinger S, Novak N. Atopic dermatitis. \emph{Lancet}
2016;\textbf{387} : 1109-22.

2 Asher MI, Montefort S, Bj\selectlanguage{ngerman}örkstén B, et al. Worldwide time trends in
the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and
eczema in childhood: ISAAC Phases One and Three repeat multicountry
cross-sectional surveys. \emph{Lancet} 2006; \textbf{368} : 733-43.

3 Kang S-Y, Song W-J, Cho S-H, Chang Y-S. Time trends of the prevalence
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4 Lee SY. Can the Use of Antibiotics Alter the Susceptibility to
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5 Song I, Park SJ, Byun SJ, Choe YJ, Shin JY. Increased use of
third-generation cephalosporin antibiotics in the outpatient setting in
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803-10.

6 Park YM, Lee S-Y, Kang M-J, et al. Imbalance of Gut Streptococcus,
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Dermatitis in Infant. \emph{Allergy Asthma Immunol Res} 2020;\textbf{12}
: 322-37.

7 Kim H-J, Lee S-H, Hong S-J. Antibiotics-Induced Dysbiosis of
Intestinal Microbiota Aggravates Atopic Dermatitis in Mice by Altered
Short-Chain Fatty Acids. \emph{Allergy Asthma Immunol Res}
2020;\textbf{12} : 137-48.

8 Bieber T. Interleukin-13: Targeting an underestimated cytokine in
atopic dermatitis. \emph{Allergy} 2020; \textbf{75} : 54-62.

9 Liu X, Nickel R, Beyer K, et al. An IL13 coding region variant is
associated with a high total serum IgE level and atopic dermatitis in
the German Multicenter Atopy Study (MAS-90). \emph{Journal of Allergy
and Clinical Immunology} 2000; \textbf{106} : 167-70.

10 Zitnik SE, Rüschendorf F, Müller S, et al. IL13 variants are
associated with total serum IgE and early sensitization to food
allergens in children with atopic dermatitis. 2009; \textbf{20} :
551-55.

11 Lee S-Y, Yu J, Ahn K-M, et al. Additive Effect between IL-13
Polymorphism and Cesarean Section Delivery/Prenatal Antibiotics Use on
Atopic Dermatitis: A Birth Cohort Study (COCOA). \emph{PLOS ONE}
2014;\textbf{9} : e96603.

12 Lee E, Kim J-H, Lee S-Y, et al. Association of IL13 genetic
polymorphisms with atopic dermatitis: Fine mapping and haplotype
analysis. \emph{Annals of Allergy, Asthma \& Immunology}
2020;\textbf{125} : 287-93.

13 Chen JG, Cai TG, Lin LY. IL-13 polymorphisms rs20541 and rs1800925 in
atopic dermatitis: a meta-analysis. \emph{Int J Clin Exp Med}
2018;\textbf{11} : 6384-96.

14 Yang HJ, Lee SY, Suh DI, et al. The Cohort for Childhood Origin of
Asthma and allergic diseases (COCOA) study: design, rationale and
methods. \emph{BMC Pulm Med} 2014; \textbf{14} : 109.

15 Jung Y-H, Seo J-H, Kim HY, et al. The relationship between asthma and
bronchiolitis is modified by TLR4, CD14, and IL-13
polymorphisms.\emph{Pediatric Pulmonology} 2015; \textbf{50} : 8-16.

16 Hanifin JM. Diagnostic features of atopic dermatitis. \emph{Acta Derm
Venereol} 1980; \textbf{92} : 44-47.

17 Severity scoring of atopic dermatitis: the SCORAD index. Consensus
Report of the European Task Force on Atopic
Dermatitis.\emph{Dermatology} 1993; \textbf{186} : 23-31.

18 Kunz B, Oranje AP, Labrèze L, Stalder JF, Ring J, Taïeb A. Clinical
validation and guidelines for the SCORAD index: consensus report of the
European Task Force on Atopic Dermatitis. \emph{Dermatology}
1997;\textbf{195} : 10-9.

19 Roduit C, Frei R, Depner M, et al. Phenotypes of Atopic Dermatitis
Depending on the Timing of Onset and Progression in Childhood.\emph{JAMA
Pediatrics} 2017; \textbf{171} : 655-62.

20 Tsakok T, McKeever TM, Yeo L, Flohr C. Does early life exposure to
antibiotics increase the risk of eczema? A systematic review.
2013;\textbf{169} : 983-91.

21 Yamamoto-Hanada K, Yang L, Narita M, Saito H, Ohya Y. Influence of
antibiotic use in early childhood on asthma and allergic diseases at age
5. \emph{Annals of allergy, asthma \& immunology : official publication
of the American College of Allergy, Asthma, \& Immunology}
2017;\textbf{119} : 54-58.

22 Oosterloo BC, van Elburg RM, Rutten NB, et al. Wheezing and infantile
colic are associated with neonatal antibiotic treatment. \emph{Pediatr
Allergy Immunol} 2018; \textbf{29} : 151-58.

23 Wickens K, Ingham T, Epton M, et al. The association of early life
exposure to antibiotics and the development of asthma, eczema and atopy
in a birth cohort: confounding or causality? \emph{Clin Exp
Allergy}2008; \textbf{38} : 1318-24.

24 Palmer CNA, Irvine AD, Terron-Kwiatkowski A, et al. Common
loss-of-function variants of the epidermal barrier protein filaggrin are
a major predisposing factor for atopic dermatitis. \emph{Nature
Genetics} 2006; \textbf{38} : 441-46.

25 Slob EMA, Brew BK, Vijverberg SJH, et al. Early-life antibiotic use
and risk of asthma and eczema: results of a discordant twin
study.\emph{The European respiratory journal} 2020; \textbf{55} .

26 Lee SC, Chua LL, Yap SH, et al. Enrichment of gut-derived
Fusobacterium is associated with suboptimal immune recovery in
HIV-infected individuals. \emph{Scientific Reports} 2018; \textbf{8} :
14277.

27 Hill DA, Hoffmann C, Abt MC, et al. Metagenomic analyses reveal
antibiotic-induced temporal and spatial changes in intestinal microbiota
with associated alterations in immune cell homeostasis. \emph{Mucosal
Immunology} 2010; \textbf{3} : 148-58.

28 Kalliomäki M, Isolauri E. Role of intestinal flora in the development
of allergy. \emph{Current Opinion in Allergy and Clinical
Immunology}2003; \textbf{3} : 15-20.

29 Kabesch M, Schedel M, Carr D, et al. IL-4/IL-13 pathway genetics
strongly influence serum IgE levels and childhood asthma. \emph{J
Allergy Clin Immunol} 2006; \textbf{117} : 269-74.

30 Foliaki S, Pearce N, Björkstén B, Mallol J, Montefort S, von Mutius
E. Antibiotic use in infancy and symptoms of asthma,
rhinoconjunctivitis, and eczema in children 6 and 7 years old:
International Study of Asthma and Allergies in Childhood Phase
III.\emph{Journal of Allergy and Clinical Immunology} 2009; \textbf{124}
: 982-89.

31 Sobko T, Schiött J, Ehlin A, Lundberg J, Montgomery S, Norman M.
Neonatal sepsis, antibiotic therapy and later risk of asthma and
allergy. \emph{Paediatric and perinatal epidemiology} 2010; \textbf{24}
: 88-92.

32 Williams HC. \emph{Atopic dermatitis: the epidemiology, causes and
prevention of atopic eczema} : Cambridge University Press 2000.

Table 1. Demographic characteristics of the study population\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
& & AD incidence at 1 year & AD incidence at 1 year &
P-value\tabularnewline
& & No (n=1089) & Yes (n=369) &\tabularnewline
History of the parent's allergic disease & Yes & 571/1087(52.5) &
208/367(56.7) & 0.169\tabularnewline
Sex & Boys & 451/904 (49.9) & 172/295(58.3) & 0.012\tabularnewline
Exposure to ETS (pregnancy) & Yes & 568/1023(55.5) & 179/346(51.7) &
0.221\tabularnewline
Delivery method & CS & 416/1084(38.4) & 127/368(34.5) &
0.185\tabularnewline
Highest education level of the mother & High school & 56/1626(3.9) &
13/289(3.5) & 0.077\tabularnewline
& University/college & 814/1626(75.1) & 265/289(71.8) &\tabularnewline
& Graduate school & 214/1626(19.7) & 91/289(24.7) &\tabularnewline
Breastfeeding at 6 months & Yes & 853/1042(81.9) & 294/358(82.1) &
0.912\tabularnewline
Exposure to antibiotics during pregnancy & Yes & 147/1029(14.3) &
48/346(13.9) & 0.849\tabularnewline
Acute bronchiolitis history within 6 months & Yes & 100/933(10.7) &
44/325(13.5) & 0.169\tabularnewline
Respiratory disease within 6 months & Yes & 105/934(11.2) & 49/325(15.1)
& 0.069\tabularnewline
AOM within 6 months & Yes & 129/1089(11.8) & 44/369(11.9) &
0.968\tabularnewline
\bottomrule
\end{longtable}

AD, Atopic dermatitis; ETS, Environmental tobacco smoke; URI, Upper
respiratory infection; AOM, acute otitis media; CS, Cesarean section

Data are reported as number (\%).

Chi-square test for proportions

Table 2. Multinomial logistic regression model for the association of
antibiotic exposure within 6 months of age with the atopic dermatitis
phenotypes.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
Antibiotic exposure within the first 6 months of life & Atopic
dermatitis phenotypes between 6 months to 5 years (reference group:
Non-AD) & Atopic dermatitis phenotypes between 6 months to 5 years
(reference group: Non-AD) & Atopic dermatitis phenotypes between 6
months to 5 years (reference group: Non-AD) & Atopic dermatitis
phenotypes between 6 months to 5 years (reference group: Non-AD) &
Atopic dermatitis phenotypes between 6 months to 5 years (reference
group: Non-AD) & Atopic dermatitis phenotypes between 6 months to 5
years (reference group: Non-AD) & Atopic dermatitis phenotypes between 6
months to 5 years (reference group: Non-AD) & Atopic dermatitis
phenotypes between 6 months to 5 years (reference group: Non-AD) &
Atopic dermatitis phenotypes between 6 months to 5 years (reference
group: Non-AD)\tabularnewline
\midrule
\endhead
& Non-AD (ref.) \emph{vs.} & Non-AD (ref.) \emph{vs.} & Non-AD (ref.)
\emph{vs.} & Non-AD (ref.) \emph{vs.} & Non-AD (ref.) \emph{vs.} &
Non-AD (ref.) \emph{vs.} & Non-AD (ref.) \emph{vs.} & Non-AD (ref.)
\emph{vs.} & Non-AD (ref.) \emph{vs.}\tabularnewline
& Early transient & Early transient & Early transient & Late onset &
Late onset & Late onset & Early persistent & Early persistent & Early
persistent\tabularnewline
& aOR & 95\% CI & 95\% CI & aOR & 95\% CI & 95\% CI & aOR & 95\% CI &
95\% CI\tabularnewline
No & 1 & & & 1 & & & 1 & &\tabularnewline
Yes & 0.97 & 0.55 & 1.7 & 1.16 & 0.62 & 2.19 & 1.84 & 1.18 &
2.86\tabularnewline
No & 1 & & & 1 & & & 1 & &\tabularnewline
Once & 0.97 & 0.51 & 1.85 & 1.25 & 0.61 & 2.53 & 1.51 & 0.9 &
2.55\tabularnewline
[?]2 times & 0.98 & 0.41 & 2.32 & 0.97 & 0.34 & 2.75 & 2.50 & 1.35 &
4.63\tabularnewline
\bottomrule
\end{longtable}

AD, Atopic dermatitis; aOR, adjusted odds ratio; CI, confidence interval

Values are presented as aOR (95\% CI) from multinomial logistic
regression models, related to non-AD.

Adjusted by sex, maternal education, family history of allergic disease,
breastfeeding, mode of delivery

\emph{P} \textless{}0.05 calculated by multinomial logistic regression
analysis.

Table 3. SCORAD score for atopic dermatitis patients at each time point
based on antibiotic exposure within 6 months of age.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
Variables & Variables & Antibiotic exposure within 6 months of age &
Antibiotic exposure within 6 months of age & p-value\tabularnewline
\midrule
\endhead
& & Yes (n=566) & No (n=1071) &\tabularnewline
AD at 6 months & Number & 77 & 110 &\tabularnewline
& Mean \selectlanguage{ngerman}± SD & 12.56\selectlanguage{ngerman}±10.94 & 14.24\selectlanguage{ngerman}±12.13 & 0.33\tabularnewline
& Mild(\textless{}15) & 49 (63.6) & 71 (64.5) & 0.90\tabularnewline
& Moderate-severe([?]15) & 28(36.4) & 39(35.5) &\tabularnewline
AD at 1 year & Number & 83 & 143 &\tabularnewline
& Mean \selectlanguage{ngerman}± SD & 9.42\selectlanguage{ngerman}±10.00 & 6.38\selectlanguage{ngerman}±9.26 & 0.02\tabularnewline
& Mild (\textless{}15) & 55(66.3) & 118 (82.5) &
\textless{}0.01\tabularnewline
& Moderate-severe ([?]15) & 28(33.7) & 25(17.5) &\tabularnewline
AD at 2 years & Number & 104 & 149 &\tabularnewline
& Mean \selectlanguage{ngerman}± SD & 7.67\selectlanguage{ngerman}±10.40 & 5.71\selectlanguage{ngerman}±9.07 & 0.11\tabularnewline
& Mild (\textless{}15) & 77(74.0) & 123(82.6) & 0.10\tabularnewline
& Moderate-severe ([?]15) & 27(26.0) & 26(17.4) &\tabularnewline
AD at 3 years & Number & 87 & 142 &\tabularnewline
& Mean \selectlanguage{ngerman}± SD & 5.85\selectlanguage{ngerman}±11.38 & 4.09\selectlanguage{ngerman}±7.89 & 0.21\tabularnewline
& Mild (\textless{}15) & 72(82.8) & 123(86.6) & 0.43\tabularnewline
& Moderate-severe ([?]15) & 15(17.2) & 19(13.4) &\tabularnewline
\bottomrule
\end{longtable}

AD, Atopic dermatitis; SCORAD, SCORing\emph{atopic dermatitis;
SD,}standard deviation

Data were expressed as number and means with standard deviation (SD) of
the estimated mean.

Student's t test for means, as appropriate.

mild AD: Score \textless{}15; moderate to severe AD: score [?]15

Table 4. Combined effects of \emph{IL-13} (rs20541) genetic variation
and exposure to antibiotics within 6 months of age on the development of
atopic dermatitis.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllllllll@{}}
\toprule
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{IL-13} genotype\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Antibiotic exposure\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 6 months\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 6 months\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 6 months\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 1 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 1 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 1 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 2 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 2 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 2 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 3 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 3 year\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
AD ever at 3 year\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
GG\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
No\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
GG\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
Yes\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.09\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.66\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.80\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.90\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.58\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.41\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.04\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.68\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.58\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.16\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.77\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.74\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
GA+AA\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
No\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.27\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.85\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.90\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.00\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.70\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.43\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.11\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.80\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.56\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.09\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.78\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.52\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
GA+AA\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
Yes\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\textbf{1.66}\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.07\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
2.57\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.55\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.05\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
2.29\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.85\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.26\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
2.70\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.83\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
1.25\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
2.69\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
Interaction p\textsuperscript{a}\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.48\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.48\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.48\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.06\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.06\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.06\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.08\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.08\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.08\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.17\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.17\strut
\end{minipage} & \begin{minipage}[t]{0.05\columnwidth}\raggedright\strut
0.17\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

AD, Atopic dermatitis; IL, interleukin; aOR, adjusted odds ratio; CI,
confidence interval

Adjusted by sex, maternal education, family history of allergic disease,
breastfeeding, mode of delivery

P\textless{} 0.05, Statistically significant differences were determined
using a two-way analysis of variance to examine the effects
of\emph{IL-13} genetic variation and/or antibiotics within 6 months of
age and/or interaction

Table 5. Multinomial logistic regression model for the association of
antibiotic exposure within 6 months of age and \emph{IL-13} (rs20541)
genetic variation with the atopic dermatitis phenotypes.\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllll@{}}
\toprule
\begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
\emph{IL-13}\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
No. of antibiotic courses within the first 6 months of life\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early transient\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early transient\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early transient\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Late onset\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Late onset\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Late onset\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early persistent\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early persistent\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Non-AD (ref) \emph{vs.} Early persistent\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
aOR\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
95\% CI\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
GG\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Never\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.00\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.00\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.00\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Once\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.64\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.20\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.04\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.05\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.79\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
5.29\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.52\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.63\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.68\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
[?]2 times\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.11\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.33\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.74\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.80\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.16\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.95\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.62\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.55\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.77\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
GA/AA\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Never\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.19\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.62\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.29\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.92\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.41\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.04\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.06\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.13\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.77\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Once\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.30\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.55\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.07\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.81\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.27\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.43\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.99\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.44\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
6.22\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
[?]2 times\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.81\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.21\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.09\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.21\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.31\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.82\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.73\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.01\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
11.14\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

AD, Atopic dermatitis; IL, interleukin; aOR, adjusted odds ratio; CI,
confidence interval

Values are presented as aOR (95\% CI) from multinomial logistic
regression models, related to Non-AD.

Adjusted by sex, maternal education, family history of allergic disease,
breast feeding, mode of delivery

\emph{P} \textless{}0.05 calculated by multinomial logistic regression
analysis.

\textbf{Figure legends}

Fig. 1. Forest plot showing the adjusted odds ratio (95\% confidence
interval) for association of incidence of atopic dermatitis at the age
of 6 months and 1 to 3 years with antibiotic exposure within the first 6
months of age.

\selectlanguage{english}
\FloatBarrier
\end{document}

