Skin testing with extracts of fungal species derived from the homes of allergy clinic patients in Toronto, Canada.

Airborne fungi in the homes of patients with allergic rhinitis or asthma, from a Toronto Allergy Clinic population, were isolated, quantified and identified to species. Allergen extracts were prepared from sixteen of these isolated species and used for skin-prick testing of twenty-six patients. Fourteen of the total patients reacted to one or more of these extracts at 1:10 (w/v) concentrations. The most common positive skin responses (8/14 to 6/14) were found for Cladosporium cladosporioides, Alternaria tenuis, C. sphaerospermum, and Fusarium sp. The two Cladosporium species were also most commonly isolated in homes, but A. tenuis and Fusarium sp. were found only in 4% and less than 1% of the air samples, respectively. Epicoccum purpurascens and C. herbarum, which were isolated on approximately 10% of the plates, showed fewer skin reactions compared with the above. Positive skin-test response to the other ten study extracts ranged from 5/14 for two species of Aspergillus and Phoma glomerata, to 1/14 for Penicillium viridicatum; of these species, Aspergillus fumigatus was isolated in 3% of the home samples, the others were less than 1%. The findings suggest that fungal antigens from species found in homes are commonly associated with skin sensitization in an allergy clinic population with upper or lower respiratory allergy. No specific relationships were found, however, between the prevalence of fungal species in the home environment and their prevalence as skin-test allergens.