Understanding Your Diet: Why are sulfates in food bad? Clarifying the Confusion with Sulfites

November 3, 2025 •

5 min read

According to the American Academy of Allergy, Asthma & Immunology, it is a common misconception that sulfates are problematic in food; the real issue for sensitive people lies with sulfites, a different group of preservatives. This article tackles the common question, "Why are sulfates in food bad?" by detailing the important chemical and dietary distinctions between these compounds.

Quick Summary

Sulfates are generally harmless, naturally occurring mineral salts, while sulfites are common food preservatives that trigger allergic-like reactions in a portion of the population. Individuals, especially those with asthma, should be mindful of sulfites and learn to read labels to manage their intake.

Key Points

Sulfites Are the Concern: The potential for adverse reactions from sulfur-based compounds in food is almost exclusively linked to sulfites (preservatives), not sulfates (natural salts).
Asthma Risk: A significant percentage of people with asthma (5-10%) are sensitive to sulfites and may experience respiratory distress upon consumption.
Allergic-Type Symptoms: Sulfite sensitivity can trigger a range of symptoms, including skin rashes, digestive issues, and in severe cases, anaphylaxis.
Labeling Requirements: Regulatory bodies mandate that food manufacturers list sulfites on labels when concentrations exceed 10 ppm, requiring careful label reading.
Sulfates Are Generally Harmless: As natural mineral salts, sulfates in food and water are non-toxic for most people, though high concentrations in water can cause temporary gastrointestinal discomfort.
Informed Choices: Managing sulfite sensitivity involves identifying common food sources like dried fruit and wine and actively checking product labels to avoid accidental exposure.

Clearing the Confusion: Sulfates vs. Sulfites in Food

Many consumers question the safety of sulfur-based compounds in their food, often conflating the terms "sulfate" and "sulfite." While they sound similar and both contain sulfur, they are chemically distinct and have very different effects on human health when consumed. Sulfates are a class of mineral salts, whereas sulfites are a group of preservatives used in food production. For most of the population, sulfates in food and water are not a concern. The potential for adverse reactions is almost exclusively linked to sulfites, affecting a specific portion of the population.

What are Sulfates?

Sulfates are salts of sulfuric acid and contain one sulfur atom bonded to four oxygen atoms ($SO_4^{2-}$). They are naturally present in many foods and are a component of public drinking water supplies. For example, magnesium sulfate, commonly known as Epsom salt, is a well-known type of sulfate. The U.S. Environmental Protection Agency (EPA) notes that sulfates are found at safe levels in most drinking water, and high concentrations (over 500 ppm) primarily affect the taste and can have a laxative effect. In dietary contexts, sulfates are generally considered non-toxic and are not typically the cause of the allergic-type reactions commonly associated with sulfur-based compounds.

What are Sulfites?

Sulfites are salts of sulfurous acid and contain one sulfur atom bonded to three oxygen atoms ($SO_3^{2-}$). They are widely used as food additives and preservatives, valued for their ability to prevent browning, inhibit bacterial growth, and maintain the color and freshness of many products. Examples of sulfite compounds include sulfur dioxide, sodium sulfite, and potassium bisulfite. These preservatives are added to a wide array of foods and drinks, from dried fruits and potatoes to wine and beer.

The Real Concern: Who is Affected by Sulfites?

The health issues surrounding sulfites are not about general toxicity but specific sensitivities in a subset of the population. The most at-risk group is individuals with asthma.

Sulfite Sensitivity and Asthma

For 5% to 10% of individuals with asthma, consuming sulfites can trigger adverse respiratory reactions, including wheezing, chest tightness, and coughing. While the exact mechanism is not fully understood, one theory is that sulfites release sulfur dioxide gas ($SO_2$) in the warm, acidic environment of the stomach, which is then inhaled and irritates the airways. Some asthmatics may also have a deficiency in the enzyme sulfite oxidase, which is responsible for breaking down sulfites. This deficiency can lead to a buildup of sulfites and subsequent reactions.

Allergic-Type Reactions

Beyond respiratory issues, sulfite sensitivity can cause a range of other symptoms in susceptible individuals, including:

Hives and skin rashes
Abdominal pain and cramps
Nausea, vomiting, or diarrhea
Dizziness and flushing
In very rare and severe cases, anaphylaxis

It is important to note that sulfite sensitivity is not a true food allergy involving an immune system response, but rather an intolerance that can cause allergy-like symptoms. For this reason, standard allergy tests are often unable to detect sulfite sensitivity, making it a condition that is diagnosed based on symptoms and dietary elimination.

Identifying and Avoiding Sulfites

Managing sulfite sensitivity requires careful attention to food labels and being aware of high-risk foods.

Common Foods and Drinks Containing Sulfites

Sulfites can be found in a surprisingly large number of processed items. Some of the most common sources include:

Dried fruits: Especially apricots, raisins, and dried mango.
Wine and beer: Used to prevent oxidation and spoilage.
Canned fruits and vegetables
Condiments: Including horseradish, mustard, and bottled lemon or lime juice.
Processed potatoes: Dehydrated, mashed, or pre-cut potato products.
Pickled products
Baked goods: Some crackers and granola bars.
Deli meats and sausages

Reading Food Labels

In many countries, including the U.S. and Canada, regulations require food manufacturers to declare the presence of sulfites if the concentration exceeds 10 parts per million (ppm). Look for these common names on the ingredients list:

Sulfur dioxide
Potassium bisulfite
Potassium metabisulfite
Sodium bisulfite
Sodium metabisulfite
Sodium sulfite

How to Navigate a Diet with Sulfite Sensitivity

If you or a family member suspects a sulfite sensitivity, these steps can help manage the condition:

Consult a professional: Speak with a healthcare provider or a registered dietitian who can help confirm a sensitivity and develop a safe eating plan.
Prioritize fresh foods: Focus on a diet rich in fresh, unprocessed foods, which are naturally sulfite-free.
Read every label: Make a habit of checking the ingredient list on all packaged foods, even familiar ones, as formulations can change.
Be cautious when dining out: In restaurants, especially those with salad bars, ask staff about the use of sulfites, as they may be used to keep food looking fresh.

Comparison of Sulfates and Sulfites


Feature	Sulfates (e.g., Sodium Lauryl Sulfate, Magnesium Sulfate)	Sulfites (e.g., Sodium Metabisulfite, Sulfur Dioxide)
Chemical Formula	$SO_4^{2-}$	$SO_3^{2-}$
Primary Dietary Use	Naturally occurring salts in water and some foods. Not typically added as a food additive.	Added as a preservative, antioxidant, and anti-browning agent.
Health Impact	Generally safe for consumption at normal dietary levels. High concentrations in water can cause diarrhea.	Can cause allergic-type reactions in sensitive individuals, especially asthmatics. Symptoms include wheezing, hives, and gastrointestinal upset.
Risk Group	The general population tolerates them well. High concentrations in water affect sensitive intestines, especially babies.	People with asthma (5-10%) and other sensitive individuals.
Regulation	Regulated in drinking water for taste, but not specifically for dietary health risks in most cases.	Must be declared on food labels if concentration exceeds 10 ppm.

Conclusion

The initial question, why are sulfates in food bad?, comes from a common but critical misunderstanding. For the vast majority of people, sulfates in food are not a health threat. The real dietary concern surrounding sulfur-based compounds comes from sulfites, which are food preservatives capable of triggering allergic-type reactions in sensitive individuals, especially those with asthma. Navigating a nutrition diet to avoid sulfites is a manageable process that starts with vigilant label reading and a deeper understanding of which foods and drinks are most likely to contain them. By differentiating between these two compounds, you can better manage your health and make informed dietary choices.

Learn more about managing sulfite sensitivity from trusted resources like the Canadian Food Inspection Agency.

Frequently Asked Questions

No, they are distinct chemicals with different structures and functions. Sulfates are salts of sulfuric acid ($SO_4^{2-}$), while sulfites are salts of sulfurous acid ($SO_3^{2-}$). Sulfates are naturally occurring mineral salts, while sulfites are primarily used as food preservatives.

For most people, no. Sulfates are present at safe, naturally occurring levels in many foods and water. High concentrations in drinking water (above 500 ppm) can cause temporary diarrhea, especially in infants, but this is a laxative effect, not a toxic or allergic reaction.

Sulfites are added to food as preservatives to prevent browning and discoloration, inhibit the growth of bacteria and fungi, and extend the shelf life of products.

Sulfite sensitivity can trigger a variety of allergic-type reactions, most notably in asthmatics. Symptoms can include wheezing, chest tightness, coughing, hives, skin flushing, abdominal pain, and nausea.

In many countries, regulations require that sulfites be declared on product labels if the concentration is above 10 ppm. You should check the ingredient list for terms such as sulfur dioxide, sodium bisulfite, or potassium metabisulfite.

Common high-sulfite foods include dried fruits (like apricots and raisins), wine, beer, bottled lemon and lime juice, canned goods, and certain condiments. Sulfites were once common on fresh produce in salad bars but were banned by the FDA for that use.

Not necessarily, but you should consult a doctor or dietitian. If you are among the 5-10% of asthmatics sensitive to sulfites, avoiding high-sulfite foods is crucial to prevent respiratory reactions. For those not sensitive, moderate intake is generally safe.

The link between sulfites and migraines is not clearly understood and more research is needed. Some individuals report headaches or migraines after consuming sulfite-rich foods like wine, but it's not a universal reaction. Keeping a food diary can help identify personal triggers.