To do so, investigators invited laboratory workers who presented any symptoms in presence of drosophila to undergo skin prick tests in order to determine if a specific sensibilization to drosophila exists. Then, a blood sample is taken from these persons to research specific IgE directed against drosophila. By this way, investigators hope determine if a specific allergy to drosophila exists, its characteristics as prevalence, symptoms, populations concerned...in order to better protect laboratory workers and prevent allergy incidence.