Exposure to domestic animals and risk of immunologic sensitization in subjects with asthma

The objective of the study was to determine whether exposure to domestic animals plays a significant role, beyond atopy, in the development of immediate sensitization to animal-derived antigens.

To test this hypothesis, 200 subjects with asthma (85 male subjects and 115 female subjects; mean age, 37 +/- 16 years) seen consecutively in an asthma clinic were enrolled in a cross-sectional survey. Each subject answered a questionnaire about allergy symptoms and past and current exposure to domestic animals. Skin prick testing with extracts of common inhalant allergens including antigens from eight species of animal (cat, dog, horse, rabbit, rat, mouse, guinea pig, and hamster) were also carried out.

Seventy-nine percent of subjects were atopic, and 91% had kept animals at home at some point (figures were 80% for dogs, 68% for cats, 23% for rabbits, and 20% for rodents). Using two-by-two tables, we showed that skin reactivity to at least one animal antigen was strongly linked to atopy (86% of atopic subjects had skin reactions as compared with 34% of nonatopic subjects: p < 0.001) but not to previous and current exposure to domestic animals (78% of both exposed and never exposed subjects). However, with the use of logistic regression, the determinants of skin reactivity to animals were atopy (p < 0.001), followed by cumulative duration of exposure to domestic animals (p < 0.01). The number of animals times the number of species times the duration of exposure was also a significant determinant of skin reactivity (p = 0.05).

We conclude that beyond the predominant role of atopy, cumulative duration of exposure to domestic animals is a significant determinant for immediate sensitization to animal-derived antigens in subjects with asthma.