If you have an allergic reaction to a prescription or over-the-counter medication, your doctor may need to perform some tests in order to confirm your allergy. These may include:

Skin testing

For some drugs, an allergy skin test can be used to uncover whether you are allergic. During a skin-prick test, a minute amount of the drug is injected into the skin—usually the back or forearm. A drug reaction will be deemed an allergic one if redness, a bump, or other noticeable skin inflammation develops. There are also intradermal tests that demonstrate Immunoglobulin E (IgE) allergies for only a few medications, among them penicillin and some other antibiotics. In this method, a small amount of the allergen is injected just under the skin and the site is monitored for a reaction. Either a skin-prick test or an intradermal test may be used, depending on the drug in question.

Drug provocation testing

In certain serious situations in which a patient’s sensitivity is not known regarding a powerful drug, provocation testing is performed; increasing doses of the drug—taken orally or under the skin—are given at planned intervals. If reaction to the drug does not indicate an allergy, the drug may be a safe treatment for the patient. The risk involved with this kind of testing includes a severe reaction, potentially even anaphylaxis.