Quantitative measurement of airborne allergens from dust mites, dogs, and cats using an ion-charging device

Background Increasing evidence suggests that children raised with an animal(s) in the house have a decreased risk of becoming sensitized. However, it is not clear whether this phenomenon is related to airborne exposure. Objective To estimate airborne exposure to animal dander and dust mite allergens using a device that can sample large volumes of air silently. Methods The device, which uses an ion-charging technique to move air and to collect particles, was run at 1.7 m(3)/min for 24 h in 44 homes with and without animals. The allergen collected was measured by ELISA for Fel d 1, Can f 1, Der p 1, and Der f 1. Results Airborne Fel d 1 was present in all homes with a cat (n = 27). The quantities measured, i.e. 0.5-20 mug in 24 h, represent 0.01-0.3 mug Fel d 1 inhaled/day at normal breathing rates (20 L/h). Values for houses without a cat were 0.01-0.05 mug inhaled/day. Airborne Fel d 1 correlated significantly with floor Fel d 1 (r = 0.58, P<0.001). Results for Can f 1 were similar in houses with a dog, but this allergen was only detected airborne in two houses without a dog. Neither Der p 1 nor Der f 1 (i.e. <0.01 mug) was detected, which represents less than or equal to 1 ng inhaled/day during normal domestic activity. During disturbance airborne mite was detected with both the ion-charging device and a filter run in parallel. For cat and mite allergens there was a close correlation between the two techniques (r = 0.84, P<0.001). Conclusion Exposure to cat or dog allergen airborne in homes with an animal can be up to 100 times higher than exposure to mite allergen. The results are in keeping with a model where immunological tolerance to animal dander allergens results from high exposure.