BackgroundAllergic reactions to insects are a global problem. The objective of this study was to assess the efficacy of immunotherapy with allergenic extract of Aedes aegypti for the treatment of large local reactions (LLR) to mosquito bites in children.MethodsExperimental, comparative, prospective, longitudinal and randomized none blinded study was conducted. We included 2 to 15 year old children with a history of large local reactions to mosquito bites. Sensitization was confirmed by a positive prick test. One group was treated with subcutaneous immunotherapy with extract of Aedes aegypti during 5 months and a second group received only antihistamine as needed. Diary symptoms and medication use were recorded in each case. The presence of adverse reactions to immunotherapy was also documented.ResultsA total of 35 patients from August 2009 to September 2010. Twenty-eight patients completed the study (16 male were included, with mean 7 ± 2.5 years) 15 in the immunotherapy group and 13 in the control group. The immunotherapy group showed a decrease in the diameter of the wheal and flare as well as the duration of the reaction and the use of drugs, from the third month of treatment, compared with the control group (P < 0.001).ConclusionsOur results suggest that immunotherapy with extract of Aedes aegypti, could modify the natural history of LLR to mosquito bites in children. Additional studies are needed to determine the optimal length treatment of the scheme and its long-term effects.