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Are sulfites good for wine? Yes. Are sulfites responsible for wine headaches? No. Are sulfites the cause of allergic reactions to wine? No, science has yet to prove otherwise. Once we understand what is known about sulfites and its love affair with wine, hopefully it will allay our fears of labeling protocol, as we frolic towards the sunset, bottles in hand, sipping what nature has given. The following is a rudimentary break down of the relationship between sulfites and the vino we love.

Take an apple and slice it open. Set it on the table and go watch an episode of BroadChurch. Come back to the table and notice how the bright juicy white flesh we love so much is beginning to turn brown. Oxygen is soaking into the fruit, oxidizing it. However, if you were to hit the apple with a significant amount of sulfur dioxide (sulfites), it would inhibit this enzymatic reaction and preserve the fruit’s color and flavor, by blocking the browning agents known as polyphenol oxidase enzymes (PPO). Sulfur Dioxide has the same effect on wine, but it’s a little more complex.

A dried apricot has at least 2000 So2 (Sulfur Dioxide) ppm (parts per million) in order to retain its structure, color, flavor and shelf life. The most a wine is exposed to is in the upper 100’s (the higher ups are more for dessert wine). So if you can take a bag of dried fruit to the face without a negative reaction, then it’s unlikely you’re allergic to SO2. It’s actually very uncommon to have a negative reaction to sulfites.  There have been a handful of cases where susceptible people have had asthmatic attacks when exposed to low levels of SO2, so while it is likely for those folks, it is very rare in general.

People do have allergic reactions to wine, but it is believed for those small amount of people who do, the main culprit for the allergic reaction is due to the histamines which also occur naturally in wine. Take a Benadryl if you feel off, and if your ship is righted then you’re one of the very few for whom the histamines in wine are the culprit.

Sulfites are good for wine and they’re a natural by-product of fermentation inhibiting oxygenation and they also encourage color extraction during the maceration process, which helps in maintaining flavor. All the wonders of wine that make us fall in love with it have to do with having a little bit of SO2 in the mix. If SO2 is not introduced into the wine, the end result can be comprised. The wine is prone to oxidation which is a catalyst to spoilage. If one does not want to use additional SO2 in the winemaking process, the best way to preserve the wine is to use pasteurization, which brings the wine to a temperature high enough to kill yeast and bacteria almost the same way SO2 does. This process does mess with the resulting complexity of a wine however. Manischewitz anyone?

Two things happen when SO2 is introduced to wine. As it interacts with the organic components during the winemaking process called must (seed, skins, juice) it breaks off into fractions. The two main fractions we are concerned with are molecular SO2 and bisulphite. Each fraction has a function. Bisulphite begins that soaking process I explained in the first paragraph, binding with up to fifty constituents in the wine. This is the stuff that preserves and enhances color and flavor. When bisulphite finishes doing its job, it is no longer a compound that concerns us, as it is rendered inactive. After the bisulphite party ends, what’s left is what is known as free SO2 or molecular SO2. This is the stuff that acts as an antimicrobial agent, killing off volatile bacteria and yeasts that have no business being in the soup – not all yeast cells propagate. This is also the stuff that, when overused, brings on that rotten egg smell. So when you see “contains sulfites” on a wine label it is determined by the total SO2 including bound and free.

Good winemakers strive to make great wine. A good winemaker knows the advantages of SO2, but wants it to be beneficial to the end product and uses caution when adding the compound. What we should be worried about when drinking wine is not the sulfur dioxide inside but the other forms of wine manipulations such as added sugars and food coloring to keep the color and flavor uniform, which are used to compensate for a lack of care in the vineyard or the winemaking process. Adding these elements along with already naturally existing compounds such as acetaldehydes (a by-product of ethanol or alcohol), histamines and glucose (the natural sugars of the wine) is thought to contribute to the headaches one feels – including hangovers. With all that said, if you do think you are sensitive to sulfites in wine, try drinking a well-aged wine, as the SO2’s influence decreases over time.