To make a diagnosis of allergic sensitization, skin tests are performed in the patient. One of the methods used is the technique of "prick test". In practice, a drop of purified allergen extract is placed on the patient's skin (arms or back). A little dosis of the product is then injected in the epidermis. If fifteen minutes later, there is an edematous reaction, its diameter is measured in millimeters. From 4 mm, it is considered that the patient is sensitized to the tested foods or allergens.This technique is painless and convenient to patients of all ages, including newborns or conversely very aged patients.