Allergy skin prick test and intradermal test represent one of the major tools in the diagnosis of IgE-mediated diseases like as atopic asthma, allergic rhinitis, atopic dermatitis, food and drug allergy, and insect bite when properly performed. Skin tests are of particular importance in fields such as allergen standardization, pharmacology, and epidemiology. Even if skin tests seem easy to perform, adequate and proper interpretation requires well-trained physicians who can recognize the numerous factors that may modify the results of skin tests.