Sulfas, or sulfonamides, are drugs, while sulfur is an element, says MedicineNet. Sulfonamides are made from sulfanilamide, which is an organic compound that contains sulfur. Its chemical formula is C6H8N2O2S, according to the PubChem Open Chemistry Database.
Sulfa drugs are mostly used as antibiotics, as they stop bacteria from using a type of folic acid to make proteins, according to MedicineNet. They are also used to treat ulcerative colitis. Examples of sulfa drugs include Bactrim, Truxazole and Sulfazine. Despite their effectiveness at fighting harmful bacteria, sulfa drugs can have severe side effects, such as nausea and vomiting, headache, dizziness, lethargy and loss of appetite. Sulfa drugs can also cause severe and even life-threatening skin rashes, including toxic epidermal necrolysis, which causes skin to blister, peel and slough off.
Sulfur is a lemon yellow solid that is necessary to life, states WebElements. It is found in bodily fluids, bones and fats, and is part of the amino acids cysteine and methionine. Deposits of sulfur are found around hot springs, volcanoes and salt domes.
Compounds of sulfur can be toxic, notes WebElements. Sulfur dioxide is a pollutant found in acid rain. Though elemental sulfur is odorless, hydrogen sulfide has a notorious rotten egg smell and is hazardous to health, says the Occupational Safety & Health Administration.