A drug allergy is the abnormal reaction of your immune system to a medication. Any medication over-the-counter, prescription or herbal, is capable of inducing a drug allergy. However, a drug allergy is more likely with certain medications. In short, Drug allergies are a group of symptoms caused by an allergic reaction to a drug (medication).
Hives Itching of the skin or eyes (common)
Skin rash (common)
Swelling of the lips, tongue, or face
Skin tests With a skin test, the allergist or nurse administers a small amount of a suspect drug to your skin either with a tiny needle that scratches the skin, an injection or a patch. A positive reaction to a test will cause a red, itchy, raised bump. A positive result almost always indicates a drug allergy. A negative result is more difficult to interpret because of differences in the reliability of tests. For some drugs, a negative test result usually means that you're not allergic to the drug. For other drugs, a negative result may not rule out the possibility of a drug allergy. Blood tests Your doctor may order blood work to rule out other conditions that could be causing signs or symptoms. While there are blood tests for detecting allergic reaction to a few drugs, these tests aren't used often because of the relatively limited research on their accuracy. They may be used if there's concern about a severe reaction to a skin test.