We report a patient who experienced systemic anaphylaxis after several mosquito bites. The skin tests were positive, by prick and intradermal tests, with two species of common mosquito (Aedes communis and Culex pipiens) and also with red midge larvae (Chironomus). Specific IgE against Aedes communis was demonstrated. We carried out SDS-PAGE and immunoblotting with whole body extracts of Aedes communis and Culex pipiens and with red midge larvae. The immunoblotting results showed specific IgE against two proteins of approximately 30 kDa with the extract of Culex pipiens. We also found IgE against one protein of a slightly lower molecular weight with Aedes communis, and against several proteins (the most important with a molecular weight between 30 and 70 kDa) with the Chironomus extract. Cross-reactivity between these insect species was suspected.