Sulfites occur naturally in wine during fermentation, and many winemakers add them to help the process along. For the past two decades, the Food and Drug Administration (FDA) has required winemakers to display the warning “contains sulfites” if levels exceed a certain threshold.

Do sulfites occur naturally?

Sulfites are the naturally occurring byproduct of fermentation. You heard me: I said naturally occurring. When yeast and sugar come together to create CO2 and alcohol, minimal amounts of sulfur dioxide are also produced in the process. Therefore, every wine will have minimal amounts of it.

Where do sulfites occur naturally?

Sulfites are found naturally in some foods, which presents an additional challenge to sensitive individuals. Peanuts, eggs, black tea, vinegar and other fermented foods contain natural sulfites. So do some otherwise healthy vegetables, including broccoli, cabbage, cauliflower, kale, garlic, onions, chives and leeks.