Antibiotics and Other Sulfonamides to Avoid If You Have a Sulfa Allergy Medically reviewed by Jurairat J. Molina, MD Sulfa drugs are synthetic (man-made) medications made from sulfanilamide that ...

A sulfa allergy occurs when a person has an allergic reaction to drugs that contain chemicals called sulfonamides. Symptoms may include a rash, difficulty breathing, and more. Sulfa is present in ...