What’s the difference between sulfates and sulfites?

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Dear Dr. Vinny,

What’s the difference between sulfates and sulfites?

—Fred, Boca Raton, Fla.

Dear Fred,

Both sulfates and sulfites are sulfur-based compounds. Sulfates are salts of sulfuric acid, and you probably encounter them on a daily basis. Sodium lauryl sulfate, a strong detergent that aids in removing grease by binding oil to water, is in everything from dish soap and floor cleaners to body washes and shampoo; some people feel it’s too harsh for body products, which is why some shampoos and other products are advertised as "sulfate-free." Epsom salts are also made of sulfates. Sulfates aren’t involved in wine production, but some beer makers use calcium sulfate—also known as brewers’ gypsum—to correct mineral deficiencies in water during the brewing process.

Sulfites are naturally occurring compounds found in all wines; they act as a preservative by inhibiting microbial growth. Consuming sulfites is generally harmless, and they are found in all kinds of things, from molasses to dried fruit. But some people—especially asthmatics—can have an allergic reaction to sulfites, which is why you see the warning that wine contains sulfites. Unfortunately, folks that experience headaches or flushing after drinking wine often wrongly blame sulfites because of that warning on the label. It causes a lot of confusion.

Even though sulfites are naturally occurring, most winemakers also add sulfur dioxide during the winemaking process to ensure against spoilage.

—Dr. Vinny

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