What Exactly Are Sulphites and Why Are They In Food?

December 28, 2025 •

4 min read

Sulphites have been used for centuries, with the ancient Greeks employing sulfur dioxide to fumigate houses and sanitize wine vessels. So what exactly are sulphites? They are a group of sulfur-based substances used as preservatives and antioxidants to prevent microbial growth, preserve color, and extend the shelf life of many foods and drinks.

Quick Summary

This guide explains what sulphites are, their purpose in food and beverage production, and the potential health effects, particularly for those with sensitivities. It details common sources of sulphites and provides clear instructions on how to identify them on ingredient labels to help sensitive individuals manage their dietary intake.

Key Points

Definition: Sulphites are sulfur-based chemical compounds used as preservatives and antioxidants in food and beverages.
Function: They inhibit microbial growth, prevent browning, and prolong the shelf-life of many processed foods.
Sources: Common sources include wine, dried fruit, processed meats, bottled juices, and some medications.
Sensitivity: Most adverse reactions to sulphites are sensitivities, not true allergies, and are more common in asthmatics.
Labeling: Food labels are required to declare sulphites if they exceed a certain concentration, so careful label reading is crucial for sensitive individuals.
Avoidance: Management for sensitive individuals involves avoiding foods and drinks containing sulphites.
Sulphates vs. Sulphites: Sulphates are chemically different and play a vital role in the human body, so people with sulphite sensitivity do not need to avoid sulfates.

What are sulphites?

Sulphites, also spelled as 'sulfites,' are chemical compounds derived from sulfur dioxide (SO2). They exist naturally in some foods and are also added to others as a regulated food additive. The term covers a group of related substances, including sodium sulphite, sodium bisulphite, sodium metabisulphite, potassium metabisulphite, and sulfur dioxide gas itself.

Historically, sulphites have been employed for their preservative qualities. In modern food manufacturing, they serve a variety of purposes that are integral to maintaining the quality, safety, and appearance of products.

The functional roles of sulphites in food

Sulphites act as a multifunctional ingredient in the food and beverage industry. Their key functional roles include:

Preservation: They inhibit the growth of bacteria, yeasts, and molds, which prevents microbial spoilage and extends the product's shelf life.
Color Preservation: By acting as an antioxidant, sulphites prevent the browning of light-colored fruits and vegetables. This is particularly important for products like dried apricots, fruit juices, and wine.
Bleaching: They can be used to bleach food starches, like potato starch, during processing.
Inhibition of Fermentation: In winemaking, sulphites are used to halt the fermentation process, which helps control the final characteristics of the wine.

Natural vs. Added Sulphites

It is important to understand the distinction between naturally occurring sulphites and those that are added during processing. All foods and beverages that contain sulphites are required to declare them on the label if they exceed a certain concentration (typically 10 parts per million or more).

Foods with naturally occurring sulphites

Some foods naturally contain sulphites as a result of their biological makeup. These can include:

Wine and beer (as a byproduct of fermentation)
Some fruits and vegetables
Black teas

Foods with added sulphites

The list of foods that may contain added sulphites is extensive. They are commonly found in:

Dried fruits: Apricots, raisins, and prunes
Processed potatoes: Dehydrated, pre-cut, or frozen potato products
Beverages: Cordials, fruit juices, soft drinks, and some ciders
Condiments: Pickled vegetables, gravies, sauces, and salad dressings
Meat products: Sausages and cured deli meats
Seafood: Shrimp and other crustaceans
Baked goods: Pie dough and some crackers

Sulphite sensitivity vs. allergy

While sulphites are safe for most people, they can cause adverse reactions in sensitive individuals. It's crucial to differentiate between a sensitivity and a true allergy, though the symptoms can sometimes be similar.

Sulphite sensitivity is the more common reaction, often triggering asthma-like symptoms, wheezing, coughing, and chest tightness. It is particularly prevalent in people with pre-existing asthma. The mechanism is not a true immune-system-mediated allergy, but rather a different type of intolerance.

Sulphite allergy is very rare and involves a true IgE-mediated immune response. In extremely uncommon cases, it can trigger anaphylaxis, a severe, life-threatening allergic reaction.

Comparison of Sulphites and Sulfates

Many people confuse sulphites with sulfates. While both are related to sulfur, they are chemically distinct and have different effects.


Feature	Sulphites	Sulfates
Chemical Formula	$SO_{3}^{2-}$	$SO_{4}^{2-}$
Oxidation State of Sulfur	+4	+6
Primary Function	Preservative, antioxidant, antimicrobial	Exists naturally in the body, aids in digestion and detoxification
Health Impact	Can cause sensitivities in some individuals; rarely true allergies	Generally harmless; crucial for many metabolic processes
Common Sources	Dried fruits, wine, processed potatoes	Many medications, soaps, shampoos, and Epsom salts

Managing sulphite sensitivity

For individuals with a diagnosed sulphite sensitivity or a history of adverse reactions, avoidance is the primary strategy.

How to avoid sulphites

Read Labels Carefully: In many countries, sulphites must be declared on food labels if they exceed 10 parts per million. Look for the terms "sulphites" or "sulfur dioxide," and check for EU codes E220-E228.
Monitor Your Intake: Keep a food diary to identify patterns and specific triggers that may cause symptoms. The level of sensitivity can vary, and some individuals may tolerate small amounts.
Opt for Fresh and Whole Foods: Whole, unprocessed foods like fresh fruits and vegetables are the safest options. Always cook your own meals from scratch to control ingredients.
Be Aware When Dining Out: Restaurant salads and other prepared foods may contain hidden sulphites used to maintain freshness and color. Always ask about ingredients.
Use Caution with Wine and Beer: Most wines and beers contain added sulphites. If sensitive, seek out brands that specifically label their products as "sulphite-free" or "no sulphites added," though trace amounts may still be present.

Alternative preservatives

Ongoing research aims to find effective, safe alternatives to sulphites for food preservation. For instance, some studies have explored plant extracts with antioxidant and antimicrobial properties. In winemaking, some producers rely on stricter hygienic practices and alternative methods to minimize or eliminate added sulphites.

Conclusion

Sulphites are common and effective food additives that play a significant role in modern food production by preserving quality, inhibiting spoilage, and extending shelf life. For the majority of consumers, they are perfectly safe. However, for a small percentage of the population, particularly those with asthma, sulphites can trigger unpleasant or even severe reactions. For these individuals, careful label reading and conscious food choices are essential for managing their health. As with any dietary concerns, consulting a healthcare professional or a registered dietitian is the best course of action for a personalized management plan.

For more detailed information on food additives and labeling regulations, you can visit the Food and Drug Administration (FDA) website for your region or the Codex Alimentarius website for international standards.

Frequently Asked Questions

Yes, sulphites can occur naturally in some foods and beverages, especially as a byproduct of fermentation in products like wine and beer. However, they are also widely used as a regulated food additive.

Common foods with sulphites include dried fruits (apricots, raisins), processed potatoes, wines, beers, bottled juices, sausages, and many sauces and dressings.

No, sulphites and sulfates are chemically different compounds, with different molecular structures and oxidation states. People with sulphite sensitivity typically do not need to avoid sulfates.

Common symptoms of sulphite sensitivity can include wheezing, chest tightness, coughing, hives, and stomach pain. These symptoms often mimic allergic reactions but are due to an intolerance rather than a true allergy.

In many countries, pre-packaged foods containing sulphites above a certain concentration must declare them on the ingredient list. Look for the terms 'sulphites', 'sulfur dioxide', or additive numbers E220-E228.

While extremely rare, sulphites have been reported to trigger anaphylaxis, a severe allergic reaction, in highly sensitive individuals. However, for most, the reaction is a less severe sensitivity.

No. Even 'sulphite-free' or 'no sulphites added' wines contain small amounts of naturally occurring sulphites from the fermentation process. For very sensitive individuals, these trace amounts may still cause a reaction.