There are all sorts of misconceptions about sulfites found in wine. Yes, many winemakers add small amounts of sulfites to preserve their wines, but sulfites are also naturally occurring. Sulfites in wine, usually red wine, get the blame for everything from headaches, sleepless nights, congestion and hangovers. Those who speak out against sulfites even claim European wines do not have any sulfites post-production, but are injected with them prior to shipping to the U.S. The confusion among the general wine-drinking community is great, but let’s look to one wine connoisseur to shed some light…
Sulfites (chemically known as sulfur dioxide or SO2) are a preservative and can be found in all wines as they naturally occur as a by-product of fermentation. Most wineries, including those in Europe and around the world, also add a minuscule amount of sulfites to preserve the color and flavor of their wines. Interesting to note that more sulfites are added to white wines, especially sweeter dessert wines, while dry red wines have the lowest sulfite content. Sulfites have been used in wine production for centuries, including to clean storage tanks after use rather than harsh chemicals.
It may come as a surprise that few countries require wine labels that state "Contains Sulfites," and less of a surprise that the U.S. is one of the handful that does. There is a tiny percentage of the population that is allergic to sulfites, mainly severe asthma sufferers, and there are many foods and beverages, other than wine, that contain more sulfites, such as dried fruit. It's a mystery why any wine made in the U.S. or imported into the U.S. must be labeled with "Contains Sulfites" while these other products with higher sulfites are not required to do so.
Bottom line: unless you are one of the few who is allergic to sulfites, the sulfites are not the cause of the “dreaded wine headache.”
- source: Fred Bowen from adeptlifestyle.com