Sulfa is found in a variety of medications, including antibiotics and nonantibiotic drugs. An allergic reaction is more likely to occur from exposure to sulfa-containing antibiotics.

Where is sulfonamide from?

Sulfonamides (sulfa drugs) are drugs that are derived from sulfanilamide, a sulfur-containing chemical. Most sulfonamides are antibiotics, but some are prescribed for treating ulcerative colitis.

How is sulfonamide created?

Sulfonamides are prepared by the reaction of a sulfonyl chloride with ammonia or an amine. Certain sulfonamides (sulfadiazine or sulfamethoxazole) are sometimes mixed with the drug trimethoprim, which acts against dihydrofolate reductase.