Sulfa is a type of pharmaceutical drug that contain sulfonamides. Sulfonamides are compounds that contain nitrogen, hydrogen, oxygen and the sulfur they take their name from. Sulfur is a chemical that is extremely small and unlikely to cause allergic reactions on its own, unlike sulfonamides.
Sulfur is a component of sulfates and sulfite preservatives, in addition to sulfa drugs. It is widely used in the production of pharmaceutical drugs and chemicals. Sulfa drugs are the first known antibiotics produced. The antimicrobial molecules inhibit the reproduction of bacteria. Allergic reactions to sulfa drugs may occur as a result of the actions of the antimicrobial molecules rather than as an allergic reaction to the sulfur in the drugs. Antibiotic sulfa drugs are more likely to cause an allergic reaction than non-antibiotic sulfa drugs.
Sulfur is a necessary part of healthy bodily function in humans. Sulfur molecules are present throughout the body and are found in essential amino acids. People who have sulfur and sulfite allergies do not have to avoid taking drugs or consuming other items that have sulfur in them because sulfur by itself is not believed to build up to unhealthy levels in the body or cause adverse reactions to consumption of the element.