If you develop a rash, hives or difficulty breathing after taking certain medications, you may have a drug allergy. While you may not experience allergic symptoms the first time you take a drug, your body could be producing antibodies to it.
Antibiotics that contain sulfa drugs occasionally cause allergic reactions. Nonantibiotic drugs containing sulfa are low risk for allergic reactions.
Anaphylaxis, a potentially life-threatening reaction that can impair breathing and send the body into shock; reactions may simultaneously affect two or more organ systems (for example, when there is both a rash and difficulty breathing). If this occurs, call 911 and seek emergency medical care immediately.
Nearly everyone knows someone who says they are allergic to penicillin. Up to 10% of people report being allergic to this widely used class of antibiotic, making it the most commonly reported drug allergy. Over time, however, the vast majority of people who once had a severe allergic reaction to penicillin lose sensitivity and can be treated safely with the drug, although 10% of individuals will remain allergic.