Distribution and determinants of house dust mite allergens in Europe: the European Community Respiratory Health Survey II

Background: Several studies in European homes have described allergen levels from the house dust mite species Dermatophagoides pteronyssinus and to a lesser extent Dermatophagoides farinae, but geographic comparisons of exposure levels and risk factors have been hampered by a lack of standardized methods. Objective: To study the distribution and determinants of the major house dust mite allergens Der p 1 and Der f 1 in 10 European countries using a common protocol. Methods: During home visits with 3580 participants of the European Community Respiratory Health Survey II from 22 study centers, mattress dust was sampled and analyzed for Der p 1, Der f 1, and Der 2 allergen. Information on housing characteristics was obtained by both observations and interview. Results: Der 1 and Der 2 allergens were detectable (>= 0.1 mu g/g) in 68% and 53% of the samples, respectively. Large differences in allergen levels between study centers were observed, and geographic patterns for Der p 1 and Der f 1 were different. Low winter temperatures reduced Der p 1 rather than Der f 1. Important risk factors for high allergen levels included an older mattress, a lower floor level of the bedroom, limited ventilation of the bedroom, and dampness for Der p 1 but not for Der f 1. Conclusion: There are large qualitative and quantitative differences of house dust mite allergen levels in Europe, which can partly be explained by geographic and housing characteristics. Clinical implications: Mite allergen exposure may be reduced by replacing the mattress regularly and increasing ventilation of the bedroom, particularly in winter.