Winemakers often supplement wines during winemaking by adding small amounts of sulfur dioxide to protect fruit quality and prevent oxidation, allowing wine to age well. Some winemakers also spray their vineyard with a sulfur compound to prevent disease and pests. Organic is the concept of making wine without adding sulfites. The result is wine referred to as “organic wine”. "Organic wines" contain only those sulfites that occur naturally.
Wines labeled “made with organically grown grapes” are made with organically grown grapes but contain more sulfites than those that occur naturally.
A derivative of sulfur, sulfites are compounds that form naturally during the same fermentation process that turns grape juice into alcohol. Because sulfites form naturally during fermentation, nearly all wines contain low levels of sulfites even when the winemaker has not supplemented or sprayed the fields. In most instances, the presence of sulfites is not noticeable. On the occasion where excessive amounts are present, undesirable characteristics described as a “biting” sensation on the throat and nose and the smell of a rotten egg may be evident.
U.S. Law dictates that wine with sulfites higher than 10 ppm must state “contains sulfites” on the label. The reason being, these sulfites can cause severe allergic reactions and/or severe headaches in some individuals.