1.1.2 Clinical evidence linking allergy to risk of viral upper
respiratory infection.
From a clinical point of view, the results are more controversial than
those from the laboratory. Studies in the literature comparing the
incidence of upper respiratory infections between allergic and
non-allergic subjects are relatively few in number (see 4 articles
included in the qualitative analyses in table II).
In two manuscript has been demonstrated that atopic/allergic patients
had increased susceptibility to upper respiratory infections. In 2006,
in a large cross-sectional survey Karevold et al.(21)demonstrated that atopy increases the risk of developing upper and lower
respiratory tract infections in children. In particular, atopy was the
strongest risk factor, such as in the home environment (dampness).
Accordingly, Ciprandi et al.(22) observed that
allergic children have a significantly higher number of upper
respiratory infections, more serious in duration and severity, compared
with non-allergic ones.
Other authors disagree: Kværner et al.(23) reported
that correlation between upper respiratory infection and atopic diseases
from a population-based sample of 7992 Norwegian twins was weak, even
though results were inconclusive. Sütçü et al.(24)confirmed that the number of episodes per year was not significantly
different between atopic and healthy children, even though atopic ones
had longer episodes of recurrent URTI compared to controls.
Interestingly all clinical studies included in the qualitative analyses
about therapy (Table II) supported the hypothesis that anti-allergy
specific or non-specific treatments may prevent viral infections of the
upper airways. Antihistamine therapy can act by reducing the expression
of adhesion viral receptors to modulate the production of TH-2 related
interleukins(22). Authors(16,25)demonstrated that children treated with cetirizine had a significant
reduction in ICAM-I expression on epithelial cells, thus preventing
possible relapse of rhinovirus infections and diminishing both the
number and severity of recurrent respiratory infections in children.
Barberi et al.(26, 27) demonstrated that children
treated with sublingual immunotherapy (SLIT) had significantly fewer
respiratory infections (RI) than symptomatically treated children. In
addition, SLIT-treated children had less fever episodes per year and
took fewer medications vs. symptomatically treated children.