Sulfates are an enormous group of chemicals that contain the element sulfur. The human body contains dozens of sulfate compounds, and there are hundreds of sulfates in a natural foods diet. You cannot be allergic to sulfur, as it is a natural part of every cell in your body. Occasionally, however, people are allergic to the OTHER end of a sulfate molecule. Someone allergic to shellfish, for example, may be allergic to glucosamine sulfate because glucosamine is derived from shellfish.
Sulfa drugs, (sulfanilamide, sulfathiazole, sulfadiazine and about a hundred others) are a class of pharmaceuticals called sulfonamides, which are the amides of sulfonic acid. They are useful because they stop bacterial growth, even if they don’t actually kill bacteria like antibiotics. Some people are allergic to sulfa drugs, but this does not carry over to sulfate compounds. I’ll say that again: there is no connection between sulfa drugs and the sulfates found in your body, your dinner, or your nutritional supplements.
Sulfites are sulfur-containing chemicals used as food preservatives, such as sodium metabisulfite. Again, they are entirely different from sulfates and sulfa drugs. Some people, especially asthmatics, are sensitive to sulfites and can experience severe allergic reactions. Since 1987, food containing more than 10 parts per million (ppm) sulfites and drugs containing sulfites must be labeled.