Chances are, the wine you drank last night had a "contains sulfites" advisory on the label. Ominous as that may sound, sulfites are a terribly misunderstood component of wine. We’ve set out to demystify a few sulfite myths here.
– First let me say that just as some people are lactose intolerant or allergic to pollen, there are people who are sensitive to sulfites, even the small amounts in wine (which contains about 10mg/glass; 80mg/liter), and this sensitivity can cause a reaction. Asthmatics can be particularly sensitive. This small percentage of the population must also avoid other sulfite- heavy products such as dried fruits and molasses. If you think you're sensitive to sulfites, try eating a handful of dried apricots and see how that affects you – dried fruits, particularly apricots, have about 10 times more sulfites added than your regular glass of wine.
– Sulfites are not the cause of the mysterious red wine headache. Some drinkers do get a headache from red wines, but studies have not yet been able to find the exact culprit there, though histamines are thought to have some effect. White wines often have more sulfites than reds, so if no headache is caused by whites, but you do get them with reds, its not the sulfites.
– Almost ALL wines contain some percentage of sulfites. Yeasts naturally create sulfites in wine during fermentation, so if your wine was fermented, then its got some sulfites hanging around. What the USDA’s advisory label primarily refers to are added sulfites.
– Sulfites are added to wine as a preservative since wine is a perishable substance. They are not dangerous. They have been a part of winemaking for centuries, though in different forms. They kill bacteria in wine, which we certainly don’t want, and they protect the wine from oxygen, which can turn a wine to vinegar pretty fast.
– Almost all winemakers add some sulfites to their wines. Again, winemakers want to preserve their wine, and sulfites are the safest way to do it. You can find wine with no added sulfites, which can be stated on the label. These are the only wines can be certified organic by the USDA. There are other organic certification programs that do allow minimal sulfites to be added.
– There is no difference in the French or Italian wine you drink here vs. the one you drank in the home country. Winemakers do not add more sulfites in wines coming to the US than they do to wines that remain local. Most other countries do not require a sulfite warning on the label, so you will only see the warning on wines purchased in the US. But again, that does not mean that a Bordeaux here in the US has more sulfites than the Bordeaux sold in Bordeaux. Just the labeling laws differ.
So, those are some notes on sulfites. A great article to read on sulfites and wine is here, done by researchers at UC Davis.