Sulfites are a group of chemical compounds found naturally in some foods and added to others as a food preservative. They are also used in winemaking to preserve freshness, prevent oxidation, and maintain the wines color and flavor. Sulfites are produced during the fermentation process of winemaking, and winemakers have been adding sulfur dioxide to wine since the 1800s. Almost all wine contains sulfites, and in the United States, wines that contain 10 or more parts per million (ppm) of sulfites must state on the label that they contain sulfites. However, most wines average about 80 ppm of sulfite, and dried fruits typically contain 1000 ppm of sulfite while French fries contain 1900 ppm.

Sulfites are used throughout the food industry as a flavor enhancer and food preservative, and they are especially important in the winemaking process. They can help prevent the wine from browning, inhibit bacterial growth, and sanitize equipment used in wine production. Most people can safely consume the sulfites found in wine with minimal risk of adverse side effects. However, some people may be sensitive to sulfites and experience symptoms such as headaches, hives, or difficulty breathing. Red wine typically contains fewer sulfites than white wine or dessert wines, and some winemakers now make low-intervention wines that are more natural and devoid of chemicals, including sulfites.