You see it virtually every time you pick up a wine bottle, Contains Sulfites. What does this mean? Is it bad for you? Why does wine contain sulfites? Sulfites (sulfur containing compounds) are a byproduct of the fermentation process but additional sulfur dioxide is added to wine to guard against oxidation and microbial growth (bacterial or yeast). It also preserves freshness and color (anthocyanins). By law, a winery must put this warning on their labels if their product meets the legal threshold of 10 parts per million (ppm). Some people state sulfites are culprits for hives, swelling, stomach pains and headaches. The FDA states the percentage of the population that is sensitive to sulfites is about 1%. Wine, however, is not the only product that contains sulfites. Do you ever eat raisins or prunes? They typically have 500 to 2000ppm. If you can eat these foods without an issue, it is not the sulfites in wine that are causing you issues. Another factor to consider is that the side effects of sulfites they list are also common issues some have with other components of wine, such as tannin or histamines. If you still want to avoid sulfites, you can seek out natural wines, but keep in mind, without sulfur, microbial growth can affect the wine. No wine will be completely free of sulfites as they are still a naturally occurring compound.
-TheLooseTannin
A Trip Around the World of Wine in 52 Weeks 