What Are Sulfites and Why Do Wines Have Them?

Few topics in the wine industry fuel as much controversy as sulfites. These compounds are blamed for everything from flushed cheeks to morning-after headaches and plenty of alleged issues in between. It’s raised questions about why wines contain sulfites at all. 

Wine educators swear that sulfites are misunderstood. But how do sulfites end up in wine? And what do these compounds do? We consulted with wine specialists to help break this down.

What are sulfites?

Sulfites are chemicals used as preservatives, according to the Cleveland Clinic. Sulfites occur naturally in some foods and drinks, while they are added to others. Sulfites help keep food, drinks, and medications from spoilage or discoloration. 

“Almost all organisms have sulfites because they’re naturally occurring,” says Andrew Bell, wine educator and president of American Sommelier, an educational and advocacy group. While they’re easily confused, sulfites differ from sulfur, sulfa drugs, and sulfates. 

While the back of a wine bottle may say “contains sulfites,” only bottles that contain more than 10 parts per million of sulfites must carry this label, per the U.S. Food and Drug Administration (FDA).

Why do wines have sulfites?

There are a few reasons why wines contain sulfites.

“While small amounts are often created by the yeast, most sulfites occur due to the addition of sulfur dioxide during the winemaking process,” says Timothy Buzinski, assistant professor of wine and beverage studies at the Culinary Institute of America. 

Sulfur dioxide, a type of gas, is used to prevent oxidization and bacterial development in wine, says Buzinski. It can even reverse the effects of oxidation, he says.

But sulfites appear in wine, regardless of intent. “Sulfites will be in wine, whether sulfur dioxide is used or not,” says Diego Meraviglia, president and director of education for the North American Sommelier Association. “Most people don’t realize this,” he says. “Sulfites are a naturally occurring byproduct of fermentation.”

Sulfites are necessary, “unless you want to drink wine that’s oxidized, brown, smells of barn, and probably has a lot of flavors you won’t enjoy,” says Meraviglia. “If you want to age your wines, you absolutely want sulfites to be added.”  

Though sulfites occur naturally in wine to some extent, sulfur dioxide may have been added to wine as far back as the ancient Romans.

“There is some belief that the Romans burned candles to allow the sulfur to purify wine vessels,” says Buzinski. “The first recorded use of sulfur dioxide in winemaking dates to the mid-1400s.”

Can sulfites make you sick?

Sulfites can cause allergies or sensitivities, says Purvi Parikh, MD, an allergist with Allergy & Asthma Network. However, this is rare. Reactions can be more common in people with asthma. Data suggests that around 5% of people with asthma also have a sulfite sensitivity. 

Symptoms include wheezing, shortness of breath, chest tightness, coughing, sneezing, a stuffy or runny nose, and hives.

People can also lack an enzyme, aldehyde dehydrogenase, which helps to break down alcohol in the gut. Some may confuse this for a sulfite allergy, says Parikh. “This can cause flushing, which may be mistaken for an allergy,” she says.

Those with an allergy to sulfites in wine would also likely react to foods like dried fruits, French fries, and packaged snacks. These foods have greater concentrations of sulfites, says Meraviglia. “If you’re not getting a massive headache after eating dried fruit and nuts, you can’t be getting a headache from sulfites in wine,” he says. 

“It’s important to remember sulfites, and the use of sulfur dioxide, became an issue when it was recognized as an allergen,” says Buzinski. “However, many foods have significantly higher levels of sulfites than wine, even conventional wines.”

What are the current trends around sulfites in wine?

Some companies suggest that their wines are sulfite-free. But Meraviglia stresses that “there’s no such thing as a sulfite-free wine on earth.”

Those that market their wines more accurately will claim that they don’t add sulfites, or that their product is low in sulfites.

“They know it’s impossible to say ‘sulfite-free,’” says Meraviglia. 

Plenty of winemakers have looked to reduce their sulfur dioxide usage.

“Since sulfites escape over time, small additions are added to keep the wine safe from microbial spoilage, but never exceeding certain thresholds,” says Buzinski. “Others have limited the use to a bare minimum, perhaps only at bottling.”

Producers in the natural wine category may skip commercial yeasts in favor of ones naturally present in the vineyard and winery. However, many use some sulfur dioxide in the winemaking process.

Do you need sulfites in wine?

Wine educators say that some sulfites are needed in wine. “They prevent spoiling and flavors we don’t want,” says Bell. “They serve as a protectant for wine during the aging, shipping, [and] stocking [processes, as well as] exposure to sunlight, temperature variations, and anything else that can damage and spoil the wine.” 

However, the amount of sulfites used now is often less than in the past. “There’s been a dialing back in the use of sulfites because technology and cleanliness have improved,” says Meraviglia. 

If you’re concerned about sulfites, Bell recommends to look for winemakers that don’t add sulfites. or those that limit their use. Just be aware that these wines may taste different from what you’re accustomed.

“This wine is attempting to be as sanitary and focused as possible without adding agents that may add shelf life to the wine, and should be drunk young,” he says. 

Buzinski agrees. “There are many examples of successful wines made without sulfur, but also others that could be improved by a small addition,” he says.