Sulfites are one of the most misunderstood components in wine. You’ve probably seen “contains sulfites” on the label and wondered—what are sulfites? Are they bad? Do they cause headaches? In this guide, we’ll explain what sulfites are, why they’re used in winemaking, how they affect taste, and whether they’re something you should be concerned about.

What are sulfites?

Sulfites (or sulfur dioxide, SO₂) are chemical compounds that occur naturally during fermentation and are also commonly added to wine as a preservative. They help prevent oxidation, preserve freshness, and protect against unwanted bacteria and yeast.

Sulfites are found not only in wine but also in foods like dried fruits, canned soups, pickles, and even salad bars.

Natural vs. added sulfites

All wines—yes, even natural wines—contain some level of naturally occurring sulfites produced during fermentation. However, many winemakers choose to add additional sulfites for stability, longevity, and consistency, especially in commercial wine production.

• Natural sulfites: Formed during fermentation (typically 10–40 mg/L)

• Added sulfites: Winemakers may add up to 150 mg/L in red wines and up to 200 mg/L in white wines (higher limits in sweet wines)

In contrast, natural wines or low-intervention wines often contain little to no added sulfites. These wines can be less stable and more sensitive to spoilage—but also appeal to those looking for a "cleaner" or more "alive" wine.

Why are sulfites added to wine?

Sulfites play a crucial role in winemaking for several reasons:

1. Prevent oxidation – Sulfites slow down the wine’s contact with oxygen, keeping flavors fresh and vibrant.

2. Stop fermentation – In some cases, winemakers use sulfites to halt fermentation at a desired sweetness level.

3. Protect against bacteria and spoilage – Sulfites keep wine safe by killing unwanted microbes and wild yeasts.

4. Preserve color and clarity – Especially important in white wines, which are more susceptible to oxidation.

Do sulfites affect the taste of wine?

In small, controlled amounts, sulfites do not negatively affect the taste of wine. In fact, they help preserve the wine’s intended character over time. However, excessive use can lead to off-flavors, such as:

• A sharp, chemical-like edge

• Suppressed fruit aromas

• Muted freshness

In natural or low-sulfite wines, you may notice more vibrant, raw, and sometimes unpredictable flavors—both a benefit and a risk depending on the winemaking quality.

Are sulfites in wine bad for you?

For most people, sulfites are completely harmless. However, a small percentage of people—particularly those with asthma or sulfite sensitivity—can have reactions. It’s estimated that only about 1% of the population is truly sensitive to sulfites.

Symptoms of sulfite sensitivity

• Headaches

• Flushing

• Hives or skin irritation

• Wheezing or asthma-like symptoms

• Stomach discomfort

If you suspect you're sensitive to sulfites, consult a medical professional. Keep in mind that headaches are more commonly caused by histamines, dehydration, or alcohol, not sulfites.

Do red or white wines have more sulfites?

Surprisingly, white wines often contain more sulfites than red wines. That’s because red wines contain tannins and antioxidants from grape skins, which act as natural preservatives. White wines are more fragile and typically need more sulfite protection.

• Lower sulfites: Dry reds (like Pinot Noir, Syrah), natural wines

• Higher sulfites: Sweet wines, white wines, sparkling wines

How to avoid sulfites in wine

If you're looking to reduce your sulfite intake, here are some tips:

• Choose natural wines or wines labeled “no added sulfites”

• Look for certified organic wines, which often have lower sulfite levels

• Drink dry reds with minimal processing

• Explore low-sulfite producers—your local wine shop or the Swirl app can help

The Swirl perspective: Sulfites decoded

At Swirl, we believe that wine should be both enjoyable and transparent. Whether you’re sensitive to sulfites or just curious, our app can help you discover wines with lower sulfite levels, understand their taste profiles, and find producers who align with your preferences. Wine is personal—Swirl helps you make informed, confident choices.