Sulfites are a naturally occuring compound that nature uses to prevent microbial growth. They are found on grapes, onions, garlic , and on many other growing plants . Winemakers have been adding additional sulfites to wines for millenia. The Greeks and Romans used sulfur candles to sterilize their wine barrels and amphorae. Sulfur protects damage to the wine by oxygen, and again helps prevent organisms from growing in the wine.
Sulfite allergies are a problem for some wine drinkers.
For them, the sulfites can lead to serious headaches. White wines have more sulfites than red wines, so this can be a way to determine if sulfites might be the problem. Sulfites, used improperly, can also give a rotten- egg smell to a wine. There is no consensus on any other problems caused by sulfites. A wine without sulfites is drinkable by those allergic to sulfites.