Relevance of allergens from cats and dogs to asthma in the northernmost province of Sweden: Schools as a major site of exposure

Background: The prevalence of asthma in the northernmost region of Sweden h as been estimated at 6% to 8% in spite of the very dry climate. The causes of the increase in asthma are not clear, but conditions are unfavorable for dust mite growth, and domestic animals are thought to be the primary sourc e of indoor allergens. Objectives: We sought to investigate the relationship between asthma, expos ure, and sensitization in Northern Sweden, with a focus on the role of scho ols. Methods: Serum was collected from 110 asthmatic children, 55 children with symptoms of asthma but no established diagnosis, and 63 control children (a ge, 7 and 8 years). Total IgE and specific IgE to 7 allergens were measured . Dust samples were collected from the classrooms of 7- and 8-year-old chil dren in 22 schools from Kiruna and Lulea, Sweden. For comparison,. dust was also collected from 24 homes in Kiruna and 2 schools: in Virginia in the U nited States. Results: Serum IgE antibody assays on 165 children with respiratory symptom s confirmed that there was a high degree of sensitization to cat, dog, and birch in Northern Sweden. Cat and dog allergens were present in almost all of the school samples in Sweden. By contrast, dust mite and cockroach aller gens were generally unmeasurable. The highest levels of cat and dog allerge ns were found in samples from desks and chairs. Cat and dog allergen levels in the schools were comparable with but higher than those in the homes wit hout pets, The schools in Virginia had similar allergen levels, except that samples from this humid region also had significant mite allergen. Conclusions: In this climate the primary sensitization associated with asth ma is to cat dander and dog dander but also to birch pollen. Mite and cockr oach allergens were not present in the dust samples, and sensitization to t hese allergens was not significant, The schools appear to be a major site o f exposure to cat and dog allergens. These results are relevant both to an understanding of the reasons for the increase in asthma in this region and to any proposal to reduce exposure to allergens.