Imported fire ant allergy in young children: Skin reactivity and serum IgE antibodies to venom and whole body extract

Abstract We studied 19 young children (aged 15 to 39 months) who had had a systemic allergic reaction after imported fire ant (IFA) sting. Skin testing was performed with whole body extract (WBE) of both Solenopsis species; positive reactions to S. invicta was noted in 94% and to S. richteri in 100%. Serum was tested for total IgE level and for specific IgE antibodies by RAST with WBE and venom (V) of S. invicta . In vitro results were compared with those of 19 age and sex-matched atopic control subjects. The range of total serum IgE level was 31 to 1720 IU/ml (geometric mean 160 IU/ml), compared with 7.5 to 6756 IU/ml (geometric mean 85 IU/ml) in the control subjects. The difference between the two groups, however, was not statistically significant ( p > 0.05). In the IFA-allergic group, the IFA WBE RAST mean binding was 13.5% (range 2.0% to 30.2%), and the IFA V RAST mean was 29.2% (range 7.8% to 46.7%). The control sera demonstrated low levels of activity to both IFA WBE RAST (0.7% to 4.8%) and IFA V RAST (0.7% to 5.9%). IFA WBE RAST demonstrated that 26% of the IFA-allergic patients had counts within the range of the atopic control subjects. In contrast, the IFA V RAST clearly separated all IFA-allergic patients from their age and sex-matched atopic control subjects. A scoring system for IFA V RAST is proposed. These results demonstrate superiority of IFA V over IFA WBE RAST in the diagnosis of allergy to S. invicta .