Drug allergy testing

Testing for hypersensitivity drug reactions depends on the underlying mechanism involved. These are commonly divided into reactions which are considered immediate, occurring within a few hours and those which are nonimmediate or delayed in onset. Obtaining an accurate and thorough history of the drug exposure, symptoms, required treatment, and subsequent exposure to the same or structurally similar drugs will help guide the clinician’s approach to possible testing. Skin testing with skin prick and intradermal testing (IDT) is appropriate in evaluating immediate hypersensitivity drug reactions. This testing is followed by an oral challenge to the drug, ensuring tolerability. In certain circumstances, direct oral challenge without preceding skin testing may be appropriate. The approach to testing nonimmediate/delayed reactions is less well defined but often involves in vivo testing such as patch testing or delayed reading of IDT or in vitro testing methods.