A case of anaphylactic shock caused by an Argas reflexus sting in a young woman with a history of recurrent undefined urticaria-angioedema syndrome, is reported. This tick is an ectoparasite which is found on pigeons who usually nest under the roofs of dwellings. The diagnosis was based on the history and through a dosage of IgE specific antibodies with RAST, using an extract of salivary gland of Argas reflexus. This ectoparasite was also found in the home and identified through the microscope. It is known to be the potential carrier of the Borrelia burgdorferi, which is the vector of
Lyme disease. In our case Argas reflexus caused IgE-mediated reactions and therefore this hypothesis must be considered in the investigation of urticaria-angioedema syndrome or anaphylactic shock in patients who live in houses with pigeons’ nests.