Sulfa allergy is the allergic response that occurs from the presence of the compound structure SO2NH2. This compound can be found in the molecular makeup of many different drugs. The term "sulfa"

Sulfa antibiotics are used to treat many common infections, but this drug class can cause a variety of side effects. A common oral formula, called TMP-SMX (Bactrim or Septra) combines sulfamethoxazole with the antibiotic trimethoprim.