Sulfites are usually added to wine as a preservative / stabilizer. What the sulfites (like potassium metabisulphite) do is to release a bit of sulfer dioxide into solution which both kills and inhibits the growth of certain yeasts, mold and bacteria. It also helps slow down oxidation in wines.

Sulfites are naturally occurring during wine fermentation in small amounts and wine makers add some more (in the parts per million range, if I remember correctly) to help make sure that the wine doesn't do things like turn into vinegar in the bottle.

What harm they can do depends on if you are allergic / sensitive to sulfites. For most people, there is no reaction at all and no harm is done (things like dried fruit have at least as much sulfite added). If you have an allergy or are very sensitive to sulfites, the usual reaction is something like an asthmatic attack - your throat begins to tighten and it gets a bit tougher to breathe. In severe allergic reactions, you could be sick for days or be sent to the hospital to get help breathing but this is relatively rare unless you know you have an allergy - kids usually have raisins with sulfites before they have a glass of wine ;).

I am mildly allergic to sulfites. Dried apples with sulfites added to prevent browning will set off the asthma-like response mentioned by Makalu. Many fresh salsa preparations have enough sulfites to cause me trouble. Fortunately it passes quickly.

On the other hand, several glasses of wine will give me a slightly stuffy nose. Obviously the amount present is very small. It is possible to buy wine without sulfites in healthfood stores and better wine stores.

They also cause head-aches in some people.

Headaches?? Was visiting my cousin in the Baltimore area (he makes his own). . .we consumed copious bottles of red. . .no headaches. I asked him if he knew why. . .and he said most home vintners use less sulfites than commercial bottlers and that sulfites can cause the headaches. How I wish I could bring back cases of his stuff!!

I had a roommate who dated a Napa winemaker... once he came over and spent the night before showering after work. The next morning she had the worst hives I have ever seen in my life, we inspected her bed, found sulfite crumbs. (what did he do roll in the stuff?) we changed the sheets... when she woke up the next morning after that with the same hives, we had to flip the mattress. I don't do sulfites anymore.

Aerating the wine in a large open container will frequently allow the sulfite gas to dissipate. Like most foods read the label too.

Just about any red wine has sulfites in it whether it says so on the label or not. Even if there isn't any sulfite added to the wine, yeast generate some so2 as a matter of course. But potasium metabisulfite is pretty much a requirement for making red wine.

Sulfites get a lot of undeserved bad reputation. It's usually NOT the sulfites that give people headaches.

Is adding Sulfites a U.S. thing? My wife travels to France 4 -5 times a year and always brings back wine. I don't want to sound snobbish but a 5 euro bottle from France is usually better than a $40 bottle form here.

eggafooz - no.

Sulfites can be naturally occuring. In addition, sulfur is added to the wine to prevent oxygenation. Oxygen is bad for wine and will ruin it. So some people add a lot of sulfur. In addition, the grapes are often dusted with "Bordeaux mixture" to prevent disease, which is copper and sulfur and was developed in France, so even if nothing is added, the juice will have sulfur.

UC Davis preached clean winemaking, so wineries in the US are physically quite clean - not the case in Europe, where they range from clean to filthy. But filth adds another element. In Chateauneuf du Pape, for example, the wineries are not clean and a lot of what we consider a typical aroma is actually due to brettanomyces.

In addition, CdP usually includes a great deal of grenache, which is a fantastic grape. However, it is prone to oxidation so winemakers add more sulfur than they might if the grape were cab sauvignon, for example.

So you get sulfur compounds from lots of places.

Some people claim that it gives them headaches. Possibly. But the amounts added tend to be small. I think most of those people just have the headache from the alcohol.

As far as a 5 euro bottle being better than a $40 bottle here - come on. A statement like that can't really be serious. I generally taste several thousand wines a year from all over the world. So I have a pretty good idea of what a 5 euro bottle is like from most winemaking countries in Europe.

I have asthma and have noticed that I have an occasional asthma attack shortly after drinking red wine due to the sulfites. Not a huge deal, I just try not to drink too much of it.