Clinical and Laboratory Profile of Patients with Anaphylaxis To Fire Ant Venom ( Solenopsis sp.) Under Subcutaneous Immunotherapy

Anaphylaxis to fire ant venom ( Solenopsis sp.) is a significant cause of systemic allergic reactions caused by Hymenoptera stings in children. There are only a few reports regarding the safety and efficacy of specific immunotherapy. We evaluated clinical characteristics (IgE and IgG4) of patients undergoing immunotherapy with a whole-body extract of Solenopsis sp. after 1 year of the maintenance phase. Thirty-three patients with severe anaphylaxis from fire ant stings ( Solenopsis sp.) were recruited and underwent venom immunotherapy. They were assessed at baseline and 1 year after beginning the maintenance phase with a skin test determining specific IgE and IgG4 antibodies to fire ant venom and tryptase. Although two patients (6.25%) presented a tryptase level higher than 11.4 µg/mL, systemic mastocytosis was ruled out. There was no relationship between reaction severity and gender, tryptase level, atopy, previous reactions, concentration of the allergen in the skin test, or specific IgE level. There was an increase in the specific IgG4/IgE ratio between the baseline and the end of the maintenance period. Reactions were local during the build-up phase, with only two mild systemic reactions. Twenty patients suffered accidental stings during immunotherapy, with 3 presenting only urticaria. Our clinical and laboratory data show that after 1 year of the maintenance phase, patients presented significant specific IgG4 production. Furthermore, reactions to accidental fire ant stings were only mild with none being severe.