To the Editor,
The proportion of the population with allergic diseases has increased
rapidly in recent
decades1, 2. In
addition to affecting the quality of life, a significant economic burden
of these diseases was transferred to society and the national health
care system1. China is a large country with a rapidly
developing economy, wide geography, and diverse climate and lifestyles,
which may lead to significantly regional differences in the distribution
of allergens. Although a series of studies have explored the prevalence
of allergen sensitization in China, the majority of them focus on one
part of geography in China3-5. In 2009, a
study6 was conducted to estimate the prevalence of
common aeroallergens among patients with allergic asthma and/or rhinitis
in mainland China. Although the study investigated the differences of
the prevalence in different regions of China, it divided China into only
four geographical regions, which may neglect detailed information about
the characteristics of sensitization prevalence in different places in
China. In that study, the skin prick test (SPT) was used to detect the
sensitization to allergens. The method has low accuracy for positive
results because it is heavily affected by certain factors, such as the
skill of the tester, reagent used, interpretation of results and so on.
Our research has the following different characteristics compared with
previous studies: 1) covering a variety of allergic diseases, 2)
exploring both aeroallergens and food allergens simultaneously, 3)
including a large set of data from all the seven regions of mainland
China, and 4) using an internationally recognized method of sIgE
testing, ImmunoCAP, to detect sensitization. These advantages may help
us obtain more accurate and reliable results and conclusions.
Here, we conducted a large multicenter study on the prevalence patterns
of serum allergen-specific IgE (sIgE) sensitization to the four most
common food allergens (i.e., egg whites, cow’s milk, crab, and shrimp)
and five aeroallergens (i.e., house dust mite, German cockroach, tree
pollen mix, mold mix, dog dander) among 44156 patients with allergic
symptoms in 52 cities from 26 provinces of all the seven geographical
regions in mainland China from July 2015 to June 2018. The sIgE
sensitization was tested by a certified third-party laboratory service
provider with uniform and standardized procedures. This study was
approved by the ethics committee of the First Affiliated Hospital of
Guangzhou Medical University (Approval number: GYFYY-2017-18). Details
about the methods were in the supplementary materials .
Our study showed that the overall prevalence of positive sIgE responses
to the 9 allergens across mainland China from the highest to the lowest
was 33.74% for house dust mites, 24.5% for cockroaches, 19.97% for
shrimp, 17.31% for crab, 11.62% for cow’s milk, 10.92% for egg
whites, 9.35% for tree pollen mix, 4.02% for dog dander and 3.92% for
mold mix (Table 1 ). Our study confirmed that an observation
shown in several previous studies based on certain specific areas in
China3-5 that the positive cases in sIgE fell mainly
in the two low classes (i.e., classes 1 and 2) was also held in all the
seven regions in mainland China (Table 1 ).
Our study revealed the distinctive patterns in the prevalence of
allergen sensitization among regions, gender, age groups and seasons.
Geographically, there is a significant difference in the prevalence
among regions for all 9 allergens except for the mold mix (Table
S1 ). House dust mites were the allergen with the highest prevalence of
sensitization in all seven regions, with the highest in South China
(40.79%) and the lowest in Northeast China (11.21%). Allergies to
German cockroaches had a higher prevalence in southern regions
(Southwest China, South China and East China) than in northern regions
(North China and Northeast China). The prevalence of sIgE responses to
dog dander was the highest in North China and was very close to each
other in the southern regions. The prevalence of the egg whites and milk
in Central China, East China and South China was higher than in
Southwest China, North China and Northeast China, which means that
patients living in eastern, coastal and/or southern areas were more
sensitive to egg whites and cow’s milk. The prevalence of crab and
shrimp sensitization in Southwest China and South China was higher than
that in the northern regions (North China and Northeast China). The
heatmap (Figure 1 ) displays the distribution of the prevalence
of the sIgE response to allergens in different regions of mainland
China.
The prevalence of sensitization to all nine allergens was higher overall
in males than in females (Table 1 and Figure S1 )
although that may not be true in each age group for each allergen as
shown in the forest plot in Figure S1 . Our study showed that,
whereas the sensitization to egg whites and milk was the highest in
children, the sensitization to other allergens tended to be the highest
in teenagers and young adults (Figure S2 ). Figure S3displays he prevalence pattern of allergens by months across years. The
prevalence of dog dander and mold mix was very stable across months;
however, the prevalence of other allergens fluctuated from January to
December. The prevalence of house dust mites, German cockroach, shrimp
and crab were higher in the summer months (from June to August) than in
other months. The prevalence of tree pollen mix was much higher in April
and October than in other months.
This should be the first large study to investigate the prevalence of
allergen sensitization in the patients with allergic symptoms from all
the seven geographic regions of mainland China. Based on this study, we
found that the prevalence of sIgE sensitization to allergens displayed
obvious and distinctive patterns among regions, gender, age groups and
seasons. The reasons for these patterns may include lifestyle factors,
socioeconomic factors, genetic predispositions, climate, sexual
hormones, cross-reactivity and so
on3,4,6-9.
Please refer to the supplementary materials for the detailed
discussion on the factors that influenced these variations. Our findings
may help clinicians find effective individualized treatments for unique
patient groups and direct researchers to conduct further studies on the
epidemiology of allergic diseases.