Prevalence of insect allergen-specific IgE in allergic asthmatic children in Cincinnati, Ohio.

Airborne insect antigens can represent significant outdoor aeroallergens. In this pilot study, allergic asthmatic children were screened by RAST for IgE directed against common outdoor insects. Insects studied included ant, cricket, grasshopper, housefly, and moth. Spiders were also tested. Three different extraction procedures were compared to determine which method(s) best preserves the allergenic proteins. RAST discs were made for each insect extract and sera from allergic, asthmatic and nonallergic, nonasthmatic children were tested. The allergic asthmatic sera had a higher percentage of isotope binding than the nonallergic nonasthmatic sera for all insects tested. The number of subjects with a Phadebas RAST score of 2 or greater was significantly higher in the allergic asthmatic group for moth (16 of 37, 43%), housefly (7 of 30, 23%), cricket (8 of 41, 19%), and grasshopper (7 of 36, 19%). Only one of the 25 control sera had a score of 2 to moth; none of the control sera reacted to any of the other insects. Most positive sera tested showed cross-reactivity between insects. A few sera, despite showing positive RAST results to two different extracts, showed no cross-reactivity between the two extracts, suggesting that these sera contained species-specific IgE. These results indicate that a significant proportion of allergic asthmatic children have IgE that binds to extracts of moth, cricket, grasshopper, and housefly. Further studies are needed to determine whether these insect aeroallergens can produce clinically significant symptoms in sensitized atopic individuals.