Sulfur in its various forms is one of the grape grower's and winemaker's best friends, for it has a number of beneficial uses. A mixture of sulfur, lime, and water is dusted on grapes to prevent mildew, oidium, and disease; it's used to clean and sterilize winemaking equipment; sulfur dioxide is added to wine as a preservative and to prevent microbiological instability during the winemaking process; and sulfur prevents unwanted secondary fermentation in sweet wines. Small amounts of sulfites exist naturally on grapes and most other fruits, and their gaseous form, sulfur dioxide, is a natural by-product of fermentation. Even so, a winemaker normally augments the amount of sulfites present during various stages of the winemaking process with additions of sulfur dioxide (while always trying to use as little as possible). Since some people are allergic to sulfites, the U.S. government has mandated that if a wine contains 10 ppm (parts per million) or more of sulfites—and almost all wines do—its label must say "contains sulfites." A few wines are made without sulfites and will state "no sulfites added" on the label. A wine that's labeled "organic," however, doesn't guarantee that it's sulfite free. Myth: It's the sulfites in red wine that give you a headache. Fact: Red wines actually contain far fewer sulfites than white wines. The culprit may be the histamine-like compounds and other substances derived from the grape skins and tannin, but no one knows for sure. Surprising tidbit: Most dried fruit and potato chips contain higher levels of sulfites than the majority of wines.