In literature it has been described a high risk of systemic reaction after blood-sucking Dyptera bites, like mosquitoes and horsefly, in people sensitive to hymenoptera. A 51 year old man, allergic to hymenoptera venom and with a history of i.v. reaction after Mueller, who has been treated with Vespula sp. ITS for the last 3 years, was stung by a yellow, black and green insect on the neck. Five minutes after the bite, he suffered generalized hitching and urticaria, oral cavity and lower limbs paresthesia, followed by lost of consciousness. At the Emergency Room he was successfully treated with adrenaline, intravenous antihistamines and corticosteroid. The description of the insect as well as the lack of the sting on the site suggested a wasp as the culprit. By studying one of these insect that has been captured by the patient, it turned out it wasn't a Vespula, but a horsefly, the Tabanus bovinus, which resembles Hymenoptera. Skin prick test and RAST for Tabanus confirmed the allergology diagnosis. In conclusion, also Tabanus bovines can cause systemic reaction up to anaphylactic shock.