Immediate skin test reactions are the hallmark of atopic diseases. EMLA (eutectic mixture of local anesthetics) is a local anesthetic that reduces the pain and apprehension for skin testing. We studied EMLA effects on the skin prick test with allergen and histamine. Reactions were evaluated by means of wheal and flare crossed diameters, speed of reaction and local temperature changes. One hour occlusion dressing with EMLA significantly delayed the beginning of reaction with antigen (129%) and histamine (101%). It decreased wheal diameter (33% and 15%) as well as local temperature variation (55% and 80%) respectively with antigen and histamine. Local anesthesia with EMLA probably interferes with histamine action and reduces the immediate skin test reaction. Therefore, it should not be used to reduce the pain of allergy skin testing.