INDUCTION OF ATOPIC-DERMATITIS BY INHALATION OF HOUSE-DUST MITE

Background: The pathogenetic role of house dust mite in atopic dermati tis remains controversial. Recent studies have shown that intensive ep icutaneous contact of house dust mite allergen with premanipulated ski n may induce dematitis. It is, however, uncertain whether such conditi ons are met during natural contact with house dust mite. In the past, allergen inhalation has been suggested to induce exacerbation of atopi c dermatitis. The aim of this study was to investigate whether dermati tis could be induced in patients with atopic dermatitis by inhalation of house dust mite. Methods: Twenty patients with atopic dermatitis un derwent bronchial provocations with house dust mite. Challenge tests w ere performed with four concentrations of a standardized house dust mi te extract in a double-blind randomized, placebo-controlled fashion. S pirometry was performed, and FEV, runs measured before and after each challenge dose. Changes in severity or localization of itching or eryt hema were recorded. Results: In nine of 20 patients with atopic dermat itis bronchial challenge with house dust mite induced unequivocal skin symptoms after 1.5 to 17 hours. Pruritic erythematous lesions on noni nvolved sites together with exacerbations of existing lesions were see n in three patients. Three patients had an exacerbation only, and thre e other patients had new lesions only. In eight of nine patients with house dust mite inhalation-induced dermatitis, skin symptoms were prec eded by an early bronchial reaction. All patients with house dust mite -induced dermatitis had a history of asthma, and as a group they had a higher mean blood total IgE la el compared with the ''negative skirt responders.'' One patient had pruritic erythema on the placebo challen ge day, without a preceding bronchoconstrictive reaction. The number o f patients who had a skin response on the house dust mite challenge da y was significantly higher than the number of patients who had a skin response on the placebo day (p = 0.011 [Prescott's test]). Conclusions : The respiratory route may be relevant in the induction and exacerbat ion of dermatitis in a subset of patients with atopic dermatitis who h ave early bronchial reactions after house dust mite inhalation, a hist ory of asthma, and an elevated blood total IgE level. Furthermore, the se findings suggest a possible causal relationship between bronchial r eactions and skirt reactions.