Drug allergies

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Allergic reactions to medication	Anaphylaxis	Antibodies	Dermatitis, contact
Dermatitis, pustular contact	Drug rash, Tegretol	Drug rash on the back	Fixed drug eruption
Fixed drug eruption, bullous	Fixed drug eruption on the cheek	Hives

Drug allergies are a group of symptoms caused by allergic reaction to a drug (medication).

Allergic reaction - drug (medication)

In general, adverse reactions to drugs are not uncommon, and almost any drug can cause an adverse reaction. Reactions range from irritating or mild side effects such as nausea and vomiting, to allergic reactions, including life-threatening anaphylaxis. Some drug reactions are idiosyncratic (unusual effects of the medication). For example, aspirin can cause nonallergic hives (no antibodies formed), or it may trigger asthma. Only a small proportion of these reactions are allergic in nature. Many individuals may confuse an uncomfortable but not serious side effect of a medicine, such as nausea, with a true drug allergy, which can be life-threatening.

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True drug allergies occur when there is an allergic reaction to a medication. This is caused by hypersensitivity of the immune system, leading to an incorrect response against a substance that is harmless in most people. The body becomes sensitized (the immune system is triggered) by the first exposure to the medication. The second or subsequent exposure causes an immune response, including the production of antibodies and release of histamine.

Most drug allergies cause minor skin rashes and hives. However, other symptoms occasionally develop and life-threatening acute allergic reaction involving the whole body (anaphylaxis) can occur. Serum sickness is a delayed type of drug allergy that occurs a week or more after exposure to a medication or vaccine.

Penicillin and related antibiotics are the most common cause of drug allergies. Other common allergy-causing drugs include sulfa drugs, anticonvulsants, insulin preparations (particularly animal sources of insulin), local anesthetics such as Novocain, and iodine (found in many x-ray contrast dyes).

Review Date: 08/03/2005
Reviewed By: Frederic F. Little, M.D., Department of Allergy and Pulmonary/Critical Care Medicine, Boston University School of Medicine, Boston, MA. Review provided by VeriMed Healthcare Network.