Wine contains many substances that occur naturally in grapes, are created during the production process, or are added by vintners. Some of them have bad reputations, for instance, sulfite. But are sulfites actually harmful to you? And why are they in wine anyways?

What Are Sulfites?

Sulfite is also known as sulfur dioxide (chemical symbol: SO2). From a chemical point of view, it’s a salt of sulfurous acid. It naturally occurs in fruits, vegetables, and herbs. For instance, there are significant portions of sulfites in onions, garlic, or leeks, where they cause a pungent taste.

Food producers have known sulfite as a preservative for a long time. Thousands of years ago, the Romans used to burn sulfur candles inside of amphoras which were used to store foods and beverages. While burning, the candles produced SO2 that helped keep the amphoras’ content fresh.

Today, industrial food producers use sulfites for conserving dried fruits, pickled and canned foods, juices, marmalades, potato chips and similar snacks, and many other food items. And, of course, vintners use them to preserve wine.

What Do Sulfites in Wine Do?

Sulfites play a crucial role in wine. They work as preservatives that shield the wine from oxygen. That’s an essential function because oxidation encourages the growth of bacteria and fungi. These microorganisms transform alcohol into acetic acid, which gives the wine a very unpleasant vinegar-like taste and ruins it. So by preventing bacteria from growing, sulfites help keep the wine fresh and prevent it from spoiling.

Besides that, sulfites can alter a wine’s aromas and even its color. For instance, SO2 encourages the creation of thiols. These compounds give wine aromas of bittersweet fruits such as grapefruit or passion fruit, as long as they occur in small portions. So if vintners want to add these flavors to their white wines, they can use sulfites to create them.

Where Do Sulfites in Wine Come From?

Sulfites naturally occur in wine during the production process, more specifically during fermentation. When the yeast transforms the sugar of the crushed grapes into alcohol, it creates SO2 as a byproduct.

The amount of natural sulfites is relatively low, though. It isn’t enough to preserve wine for longer than a couple of months. So to increase their wines’ shelflife, vintners have to add sulfites artificially. They can do so at various stages of the winemaking process:

  • In many cases, they add SO2 soon after or even while crushing the grapes. This approach prevents bacteria that might exist naturally in the grapes from creating acetic acid. In the worst case, these bacteria can spoil wine within hours. By adding SO2 in small doses, winemakers can minimalize this risk.
  • During the first fermentation phase, sulfite levels usually drop. Thus, another addition might be necessary before continuing the process to hold off bacteria from spoiling the wine.
  • When wines age for a lot of time in oak barrels, they typically need more sulfites. Vintners check the SO2 level regularly, and if necessary, they add more sulfites to make sure the wine won’t spoil.
  • A final add-on can happen immediately before bottling. In case the sulfites level has dropped too low, winemakers increase it to the optimal level.

More Details on the Fermentation Process: HOW WINE IS MADE – THE BASICS OF WINEMAKING

Are Sulfites in Wine Bad for You?

Unlike many myths claim, sulfites are absolutely harmless for the majority of wine lovers. They don’t have any health effects, neither in the short nor in the long term.

However, a small group of people can be sensitive to sulfite. According to a study by the University of Florida, less than 1% of the population might be prone to it. The risk is slightly higher for people who have preexisting conditions. For instance, about 5% of asthma patients experience breathing problems or asthma attacks when consuming food products that contain sulfites. Other possible reactions include headaches, hives, swelling of lips and mouth, and rash.

But as said before, only very few people are affected by these problems. And if you belong to this group, you probably already know because you have suffered reactions to other food items that contain sulfites. If you’re unsure, it makes sense to talk to your doctor.

Can Sulfites in Wine Cause Headaches?

In theory, yes, but only if you are sensitive to sulfites. If you have never experienced any problems when consuming canned, pickled, or dried foods, it’s rather unlikely that you are. It’s more probable that the reason for your headaches is another component of wine, for instance:

  • alcohol
  • histamines
  • tannins

How Much Sulfite Is in Wine?

In the United States, the sulfite level in wine ranges between 5 and 350 milligrams per liter. The precise level depends on the specific wine:

  • Dry red wines of a decent quality usually have about 50 to 75 mg per liter.
  • Dry whites contain around 100 mg per liter.
  • Because of their higher sugar contents, sweet wines need more sulfites to avoid further fermentation. Sweet reds can have up to 200 mg per liter, while sweet whites and rosés contain up to 250 mg.
  • Dessert wines, especially when made from noble rot grapes, might have up to 300 mg per liter.

More Details on Noble Rot: WHAT IS NOBLE ROT AND WHAT DOES IT DO TO WINE?

For comparison, let’s have a look at other food items and their sulfite contents:

  • 1 kilogram of French fries contains around 1,900 milligrams of sulfites.
  • Canned soup ranges between 200 and 3,000 milligrams per liter.
  • Dried fruits such as figs, apricots, or dates can have up to 3,500 milligrams per kilogram.

Are There Sulfites in Organic Wine?

Yes, there are small portions of natural sulfites in organic wines. They are created during the fermentation process, so they are inevitable. But vintners don’t add sulfites artificially to organic wines. In the United States, the maximum sulfite level in organic wine is 10 milligrams per liter.
Are There Sulfites in Biodynamic Wine?
Yes. Just like organic wines, biodynamic wines contain natural but no added sulfites.

Are There Wines Without Sulfites?

No, there are no wines that are entirely free of sulfite. As it’s a compound that is created during the fermentation process, it’s impossible to make sulfite-free wine.

Some vintners try to keep the sulfite level as low as possible, though. They don’t add sulfites artificially during the winemaking process. You can find several labels on wine bottles that indicate the absence of added sulfites:

Organic Wines: According to regulations for organic winemaking by the USDA (and comparable authorities in other countries), sulfites are synthetic additives. So if vintners want to label their wines organic, they can’t use them. Besides, the natural level of sulfites can’t be higher than 10 milligrams per liter. Be aware that organic wine isn’t the same as “wine made from organically grown grapes”. For the latter, adding sulfites is permitted.

Natural Wines: Although most governments don’t regulate the use of the label “natural wine”, these wines typically don’t contain any additives. So vintners don’t increase their wines’ sulfite levels artificially.

Low Intervention Wines: Vintners who make low intervention wines (also called: minimal intervention wines) tend to follow the same procedures as natural wine producers. They abstain from sulfites as well as other additives.

Biodynamic Wines: The same is true for biodynamic wine. There are no official rules for this label. However, some private institutions such as the Demeter organization certify wines that follow specific biodynamic rules. And these rules include the prohibition of added sulfites.

No Added Sulfites Wines: This label is self-explanatory. No Added Sulfites wines (short: NSA wines) are made without additional sulfites. Unlike biodynamic or organic wines, they might contain other additives, though. Be aware that NSA isn’t a regulated label either.

More Details on Biodynamic Wine: WHAT IS BIODYNAMIC WINE AND WHY IS IT DIFFERENT?

Sulfites Level Regulations

In most wine countries, wine laws require vintners to state a warning on bottles if their wine exceeds a specific sulfite level. In the United States, that’s true for wines with 10 milligrams per liter or more. In most cases, the warning reads “contains sulfites”. But you might come across other names in the contents declaration that all refer to sulfites:

  • sulfur dioxide
  • potassium bisulfate
  • potassium metabisulfite
  • sodium bisulfite
  • sodium metabisulfite
  • sodium sulfite

By U.S. law, regular table wine can contain up to 350 milligrams of sulfites per liter. Regulations in the European Union provide specific maximum levels for different types of wine. While dry red wines can have only 150 mg per liter, dessert wines may have up to 400 mg. The following table specifies the details:

Wine Type
Wine with
max. Sulfites in Reds
150 mg/L
max. Sulfites in Whites & Rosés
200 mg/L
Wine Type
Wine with >5g sugar per L
max. Sulfites in Reds
200 mg/L
max. Sulfites in Whites & Rosés
250 mg/L
Wine Type
Late Harvest Wine
max. Sulfites in Reds
300 mg/L
max. Sulfites in Whites & Rosés
300 mg/L
Wine Type
Selected Harvest Wine
max. Sulfites in Reds
350 mg/L
max. Sulfites in Whites & Rosés
350 mg/L
Wine Type
Selected Berry Harvest Wine, Ice Wine
max. Sulfites in Reds
400 mg/L
max. Sulfites in Whites & Rosés
400 mg/L
Wine Type
Sparkling Wine
max. Sulfites in Reds
235 mg/L
max. Sulfites in Whites & Rosés
235 mg/L
Wine Type
Sekt
max. Sulfites in Reds
185 mg/L
max. Sulfites in Whites & Rosés
185 mg/L

Maximum Sulfite Levels per Wine Type according to European Union Regulations

More Details on Sekt: SEKT – GERMANY’S FAVORITE SPARKLING WINE

How to Reduce Sulfites in Wine?

You might find several products that claim to reduce sulfites in wine to make it more enjoyable for sensitive people. They come in numerous forms:

  • Purifiers to attach to the bottleneck
  • Filter membranes that look like teabags and sit in your wine glass
  • Spoon-shaped wands to swirl around in your glass
  • Liquids that you drip into your wine before drinking it
  • Sprays to apply to your glass

Whether these items actually work or not is arguable. Some wine lovers claim they do allow them to enjoy wine despite having a sulfite allergy. But others argue that the products are useless and, in some cases, cause more health problems than they solve. Also, a couple of reviewers report that their wines’ taste changed negatively after applying the filtering items.

Final Words

Sulfites are definitely not as bad as their reputation. They are harmless for most wine lovers, and they do have an essential function in winemaking. With the details from this article, you know about this function. And in case you prefer low-sulfite wine, you also know how to find it.