Skin testing is usually the preferred method for the diagnosis of immunoglobulin E (IgE)–mediated hypersensitivity because it is simple, inexpensive, and the results are immediately available. Like any laboratory test, however, a number of variables can affect the outcome, such as:

Some of these variables, such as differences in reactivity with age and sites on the body, are characteristics of the patient and are beyond the control of the operator. Other variables, such as previous use of medication, quality of the extracts, and techniques employed for performing the test, are potentially controllable by the operator, who must make informed decisions in regard to these aspects. This article reviews the evidence for these variables in the skin test response.