Atopy and house dust mite sensitization as risk factors for asthma in children.

BACKGROUND

Recent evidence suggests that asthma is not invariably related to atopy. The aim of this study was to evaluate the frequency of atopy, asthma and sensitization to eight common allergens in a large group of children with allergic symptoms.

METHODS

1426 children referred to our Paediatric Asthma and Allergy Center because of allergic symptoms were examined. Bronchial asthma, allergic rhino-conjunctivitis, food allergy and atopic dermatitis were diagnosed with standardized methods. Atopy was diagnosed if at least one skin test was positive.

RESULTS

Of the 1426 children examined, 629 (44%) were atopic and 769 (56%) were non-atopic. Asthma was diagnosed in the same proportion (i.e., 64%) of atopic and non-atopic children. However, after division into age groups, non-atopic asthma was significantly more prevalent (chi2 = 8.46) in children between 0 and 3 years old (group 1). On the other hand, atopy was significantly associated with asthma only in group 3 (odds ratio 1.85). Furthermore, a significant association with asthma symptoms was found for house dust mite (HDM) in group 3 (odds ratio 4.8).

CONCLUSIONS

Asthma is related to atopy in pre-selected children only from the age of 7 years. House dust mite sensitization seems to be an important determinant of asthma in these "older" children.