I recently attended Beer School at 21-st Amendment and an interesting question was raised. Someone asked about sulfites and which beers or what brewing processes would help reduce sulfites. The man was allergic to sulfites.
However, he incorrectly stated that different sulfur compounds in beer like Dimethyl sulfide (DMS) could break down into sulfites.
The fact is, a quality, clean produced beer should not have sulfites in it. Beer naturally produces many sulfates (SO4), but not sulfites (SO2). Sulfites are used as a preservative. It is a desirable preservative because it's a naturally occurring compound, it inhibits bacteria growth, and it reduces oxidation in wine or beer, which is very necessary. So the sulfites many people have problems with are not part of the natural brewing process, but they are because of added sulfites. But sulfites can also occur in small amounts naturally and are even sometimes added in the form of pesticides/fertilizers/bacteria inhibitors to the growing plants.
Many people have an intolerance or are allergic to sulfites. They can cause problems with breathing, especially for people with asthma. Asthma may even be caused by sulfites, but it is very hard to pinpoint. Sulfites in wine or beer can also cause bad headaches. Sulfites can also cause hives if a severe allergic reaction is triggered.
Wine is the major culprit in sulfite allergies. Grapes produce a small amount of sulfites on the outside of the grapes. The winery will crush the entire grape without thoroughly cleaning them. Wineries are not as clean as breweries - they perform a lot of their work in the open air. Fermentations are done without sterile grape juice. I've seen wooden wine barrels being filled outside once. There is a major susceptibility to bacteria and oxidation.
Breweries on the other hand are very, very clean. Beer very rarely is exposed to air. Once in the fermenter, positive pressure is present from CO2 escaping. Before the end of fermentation, the tank is sealed. It is then transferred in to a pressurized serving tank. The tank should be purged with CO2 to eliminate oxygen.
Only large breweries that have to ease sanitation practices and produce beer that may have to be stored for long periods of time in uncontrolled warehousing.
Food and beverage manufacturers must label all products with 10ppm or more sulfites in them. I have rarely seen a bottle of wine that did not have that warning on the label. I have also rarely drunk a bottle of wine that didn't give me a headache later on.
Doctors can give crude tests to see if you are allergic to sulfites. They may give you a large quantity of sulfites and monitor your reactions. They may put sulfites on your skin, then prick the skin and wait to see in hives appear.
If you are allergic, prevention is the treatment. You must learn to avoid foods with large amounts of sulfites in them. You must keep your asthma inhaler nearby and keep some epinephrine to open up the blood vessels.
Here are some links to help you learn about sulfites:
Basic overview: http://wine.about.com/library/encyc/bl_sulfite.htm
Food sources of sulfites: http://www.naturodoc.com/library/nutrition/sulfites.htm
Organic Wine Works FAQ: http://server.webwinery.com/organicwineworks/Sulfitefyi.html
FDA sight: http://vm.cfsan.fda.gov/~dms/fdsulfit.html