What is a drug allergy?
A drug allergy is an allergic reaction that occurs when the body’s immune system produces antibodies and activates disease-fighting cells in response to a specific drug. In the development of a drug allergy, the immune system is triggered by the first exposure to the medication. A future exposure causes an immune response, including the production of allergic antibodies and release of histamine. So, drug allergy reactions occur after a person has been previously exposed to the drug one or more times without any allergic reaction.