Background: Exposure to cat allergen is a major risk factor for sensitization and the development of asthma in many parts of the world. The study was designed to examine the levels of cat allergen (Fel d 1) in homes of two German cities and to detennine predictors of Fel d 1 exposure.
Methods: We collected dust samples from 405 randomly selected homes in Hamburg (n = 201) and Erfurt (n = 204). In each apartment dust samples were taken from living room floor (LR), bedroom floor (BR), and mattress surface (MA) using vacuum sampling and analyzed by two-site monoclonal antibody ELISA. Environmental variables were assessed by questionnaire to obtain information on factors supposed to have an impact on the Fel d 1 levels in house dust. The effects of possible predictors of Fel d 1 were assessed by multiple linear regression models.
Results: Fel d 1 was present in 98% of the homes (395/405), ranging from 0.015 to 7.278 microg/g dust (GM 0.486 microg/g). The levels were similar in floors (GM for LR 0.575 microg/g and BR 0.469 microg/g) and in MA (GM 0.424 microg/g). Higher allergen concentrations (> 2 microg/g) were detected in 99% of the homes keeping cats, in 55% of homes that had had a cat during the last year, and in 28% of the homes without a cat. Fel d 1 levels were significantly higher in homes with a cat (628-682-fold, MA, floor) and in homes in which a cat had previously lived (11-12-fold, floor, MA) than in homes that never had a cat. Furthermore, after controlling for possible other confounders, Fel d 1 levels were significantly higher in summer and in homes with low frequency of cleaning and low ventilation rate.
Conclusion: It could be confirmed that keeping a cat has the highest impact on Fel d 1 concentration. Besides, a continuous influx of Fel d 1 in homes without cat, as a result of direct or indirect cat contact outside the home, is likely. High frequencies of dusting and ventilation might reduce cat allergens in homes with and without cats.