Drug Allergy Overview
Allergic reaction is an uncommon and unwanted side effect of medication.
Several different types of allergic reactions to medications can occur. Reactions to drugs range from a mild localized rash to serious effects on vital systems. The body's response can affect many organ systems, but the skin is the organ most frequently involved.
An allergic reaction does not often happen the first time you take a medication. A reaction is much more likely to occur the next time you take that medication. If you have a reaction the first time, you probably were exposed to the medication before without being aware of it.
Not all adverse reactions to drugs are allergies. In fact, fewer than 10% of adverse drug reactions are allergic. Other causes of adverse reactions are interactions between two or more drugs, inability to break the drug down completely in the body (as occurs with liver or kidney damage), overdose, and irritating side effects such as nausea, vomiting, or diarrhea. If you have experienced a nonallergic drug reaction, it is important to describe it as such to medical personnel-not as an allergy. If you don't know just describe the reaction the best way that you can.
Medically Reviewed by a Doctor on 7/30/2014
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Drug eruptions can mimic a wide range of dermatoses. The morphologies are myriad and include morbilliform (most common, see Media file 1), urticarial, papulosquamous, pustular, and bullous. Medications can also cause pruritus and dysesthesia without an obvious eruption.