The incidence of atopic disease has increased 10-fold in developed countries in the last two decades [1-3]. Almost 30 percent of Americans have symptoms of upper respiratory allergy, including up to 40 percent of children and 10 to 30 percent of adults . Inflammatory processes involving IgE (IgE-mediated allergies) account for the majority of clinically significant environmental, food, and medication allergies.
There are three components to the diagnosis of an IgE-mediated allergic disorder. These are:
- Identifying the allergen, usually through a careful clinical history
- Demonstrating the presence of IgE specific to the allergen by skin testing or in vitro testing
- Establishing a causal relationship between exposure to the allergen and symptoms, either by history or with a challenge procedure
Thus, allergy testing is an important element in the evaluation of allergic disease; however, by itself, it is not sufficient to make a diagnosis. A positive test (skin or in vitro) must be supported by an appropriate clinical history of reactivity and, in some cases, allergen challenge to confirm that the suspected allergen causes symptoms.
This topic review will discuss general principles of skin testing, including indications, contraindications, factors influencing results, techniques, and accuracy. The two major methods of skin testing currently used, the prick/puncture technique and the intradermal technique, are described. The use of skin testing to diagnose specific disorders is presented in the appropriate topic reviews. (See "Diagnostic evaluation of food allergy".)