Is Sulfur Dioxide in Food Unhealthy? Understanding the Risks and Benefits

December 23, 2025 •

4 min read

Sulfites, which release sulfur dioxide, have been used as a food preservative since ancient Roman times to prevent spoilage and oxidation. While generally safe for most people, these additives can trigger adverse reactions in sensitive individuals, particularly those with asthma. This article explores the health implications of sulfur dioxide in food, its benefits, potential health risks, and how to navigate products containing it.

Quick Summary

Sulfur dioxide is a common food preservative derived from sulfites, which can cause health issues for sensitive individuals, especially those with asthma. Regulatory labeling is crucial for consumers to identify and avoid foods containing these additives, which can provoke allergy-like symptoms or severe respiratory reactions in susceptible people.

Key Points

Safety Varies: Sulfur dioxide is generally safe for most people but can cause adverse health effects, particularly in sensitive individuals and asthmatics.
Preservative and Antioxidant: The primary functions of sulfites in food are to prevent microbial spoilage and oxidative browning, extending shelf life.
Asthma Trigger: A significant percentage of asthmatics (5-13%) have sulfite sensitivity, which can trigger severe respiratory reactions like wheezing and chest tightness.
Labeling is Crucial: Regulatory requirements mandate that food products with more than 10 ppm of sulfites must declare them on the label, often with E-numbers like E220.
Common Sources: Sulfites are found in a wide variety of foods, including dried fruits, wine, processed potatoes, and certain seafood.
Sensitivity, Not True Allergy: Most adverse reactions to sulfites are sensitivities or intolerances, not true IgE-mediated allergies, although the symptoms can be similar and serious.
Not a Carcinogen: Major health organizations do not classify sulfur dioxide as a carcinogen to humans, based on available research.

What is Sulfur Dioxide and Why is it in Our Food?

Sulfur dioxide ($SO_2$) is a chemical compound commonly used as a preservative and antioxidant in many foods and beverages. It is often released by sulfite additives, such as sodium bisulfite and potassium metabisulfite, which are designated with E numbers E220-E228 in Europe. The use of sulfites became widespread in food production in the 1970s, recognized for their dual function in preserving product quality and extending shelf life.

Functions in Food Production

Antimicrobial Agent: Sulfites inhibit the growth of spoilage microorganisms like yeasts, bacteria, and molds, which helps to preserve foods.
Antioxidant: They prevent oxidation, which is the chemical process that causes food to lose its color, flavor, and freshness. For instance, sulfites prevent the browning of dried fruits like apricots and the deterioration of wine.
Bleaching Agent: Sulfites can be used to lighten the color of certain foods, such as molasses, giving them a more appealing appearance.

Common Sources of Sulfur Dioxide

Dried Fruits: Apricots, raisins, and figs are often treated with sulfur dioxide to prevent browning and maintain their vibrant color.
Wine and Beer: Sulfites are a common preservative in winemaking, protecting against oxidation and microbial spoilage. They can be naturally present or added during processing.
Processed Potatoes: Dried potato products, such as chips, flakes, and instant mashed potatoes, may contain sulfites.
Seafood and Meats: Some frozen or canned seafood, including shrimp, lobster, and clams, as well as certain processed meats like hot dogs and sausages, can contain sulfites.
Other Foods: This can include pickled vegetables, condiments, certain juices, and some baked goods.

Health Risks Associated with Sulfur Dioxide

While many healthy individuals can consume sulfites without issue, certain people are susceptible to adverse reactions. These reactions are typically categorized as sensitivities or intolerances rather than true allergies, although the symptoms can be severe.

Sulfite Sensitivity and Asthma

This is the most well-documented adverse reaction, particularly among asthmatics. Studies show that a significant portion of asthmatics (ranging from 5% to 13%) have some degree of sulfite sensitivity. The mechanism involves the inhalation of sulfur dioxide gas, which can be released from sulfite-containing food. This gas can irritate the airways and trigger bronchoconstriction, leading to an asthma attack. Symptoms include wheezing, chest tightness, and coughing.

Other Adverse Reactions

Besides respiratory issues, sensitive individuals may experience a range of other symptoms:

Skin Reactions: Hives (urticaria), itching, flushing, and dermatitis.
Gastrointestinal Distress: Abdominal pain, cramping, nausea, vomiting, and diarrhea.
Other Symptoms: Headaches, dizziness, and difficulty swallowing.

Can Sulfites Cause Cancer?

International health authorities, including the International Agency for Research on Cancer (IARC), have evaluated sulfur dioxide and found no conclusive evidence that it is carcinogenic to humans. It has been assigned to Group 3, meaning it is not classifiable as to its carcinogenicity.

Comparison Table: Benefits vs. Risks of Sulfur Dioxide


Aspect	Benefit	Risk for Sensitive Individuals
Preservation	Extends shelf life and prevents microbial spoilage.	Can cause adverse health reactions, including asthma attacks.
Appearance	Prevents oxidative browning, maintaining product color and appeal.	Potential for headaches, hives, and gastrointestinal issues.
Quality	Protects flavor and freshness, especially in wine.	Respiratory and other allergy-like symptoms.
Widespread Use	Provides an effective, cost-effective preservative for many products.	High consumption could pose increased health risks for sensitive people.

Avoiding Sulfites in Your Diet

For those with a known sulfite sensitivity or asthma, avoiding sulfite-containing products is the most effective management strategy. Modern labeling laws make this process much easier.

Tips for Avoiding Sulfites

Read Ingredient Labels Carefully: In many countries, including the EU and Canada, sulfites must be declared on product labels if their concentration exceeds 10 parts per million. They will be listed by name (e.g., sulfur dioxide, potassium bisulfite) or by their E-number (E220-E228).
Opt for Fresh, Unprocessed Foods: Whole, fresh fruits, vegetables, and unprocessed meats are naturally sulfite-free. Prioritizing these foods reduces exposure.
Choose "Sulfite-Free" Products: Many manufacturers offer sulfite-free versions of products typically treated with sulfites, such as dried fruits and wine. These products are explicitly labeled.
Be Aware When Dining Out: Sulfites can be used in restaurant settings, such as on fresh-cut produce, so it is important to ask about ingredients if you have a sensitivity.

Conclusion

For the majority of the population, consuming small amounts of sulfur dioxide as a food additive is harmless, and its preservative benefits are significant for food safety and quality. However, for a notable portion of the population with asthma or sulfite sensitivity, ingestion can lead to a range of mild to severe adverse reactions. The key for these individuals is vigilant label-reading and opting for fresh, unprocessed foods. As regulations ensure transparent labeling, consumers are empowered to make informed dietary choices that suit their health needs. When in doubt, consult a healthcare provider or allergist for personalized advice on managing sulfite sensitivity.

For more detailed information on sulfur dioxide and its health effects, refer to the CDC's Medical Management Guidelines.

Frequently Asked Questions

Sulfur dioxide ($SO_2$) is a gaseous compound, while sulfites (e.g., sodium bisulfite, potassium metabisulfite) are a group of chemical salts that release $SO_2$ and are used as food additives.

Common sources include dried fruits (apricots, raisins), wine, beer, processed potatoes (flakes, chips), pickled vegetables, and some canned and frozen seafood.

In winemaking, sulfur dioxide acts as both an antioxidant to protect against browning and an antimicrobial agent to prevent spoilage by bacteria and unwanted yeasts.

Symptoms can include wheezing, chest tightness, coughing, skin rashes (hives), flushing, abdominal pain, and headaches. In rare, severe cases, anaphylaxis can occur.

The International Agency for Research on Cancer (IARC) classifies sulfur dioxide as Group 3, meaning it is not classifiable as to its carcinogenicity to humans. There is no conclusive evidence of a link.

To avoid sulfites, you should carefully read ingredient labels for sulfites (E220-E228), choose products specifically labeled 'sulfite-free,' and prioritize fresh, unprocessed foods over packaged or processed options.

No, most sulfite reactions are sensitivities or intolerances that do not involve the same immune system pathways as a true IgE-mediated allergy. However, the symptoms can be severe and require avoidance.

While generally considered safe for healthy individuals, some studies have hinted at potential neurotoxic effects at higher intake levels. There are also reported associations with migraines and joint pain in sensitive individuals.