What we commonly refer to as sulfites (actually sulfur dioxide) is natural by-product of the wine fermentation process. It's also an antioxident and antimicrobiodal. Some wineries add extra sulfur dioxide to their wines to help preserve them and many wineries use this compound in lieu of harsh chemical like bleach to clean their vats, lines, and other wine-making apperatus.

Sulfites have gotten a rather bad reputation because a small percentage of the population-around one percent-is allergic to this compound. For this reason, any US-produced wine with more than 10ppm must include the phrase "contains sulfites" on the label. This includes virtually all wines as the naturally-occuring amount of sulfites is around 10-20ppm. (The maximum allowable amount of sulfites in wine is 350ppm.)

Wines with the lowest about of sulfites are organic wines, followed by dry red and white wines. Dessert wines and wines with a high sugar content are higher on the sulfite spectrum.

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