Identifying Sulfite Intolerances and Food Allergies

Maybe you’ve seen the ominous “contains sulfites” label on a bottle of wine, or you know someone who swears added sulfites are the cause of their hangover. Or you’re like us and know someone diagnosed with a genuine sulfite intolerance—and you’ve watched them struggle to fully avoid the compounds.

Whatever your relationship to sulfites, one thing is true: They’re everywhere. They are naturally present in all wines and beers, and they are added to processed foods as preservatives under a variety of names. So it may be a relief to know that sulfite allergies are very rare. Allergist Meng Chen, MD, of Stanford’s Allergy and Asthma Research Center, says that what she typically sees with patients falls into the intolerance category—not allergy—and even those are somewhat uncommon. “The most common reactions with sulfites are asthma exacerbations and hives,” she says.

More from Chen below on the difference between an allergy and intolerance, how allergists identify intolerances to sulfites, and ways to avoid sulfites if you need to.

A Q&A with Meng Chen, MD

What is a sulfite?

A sulfite is the name that’s given to a class of commonly used preservatives that reduce spoilage. Sometimes they’re supposed to act as antioxidants and prevent fruits and vegetables from browning. There are a number of different sulfites: sulfur dioxide, potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite, sodium sulfite…pretty much anything that ends in “sulfite.”

Sulfites are different from sulfates. Sulfates are sulfuric acid, and they are present in many medicines, supplements, and personal-care products. Then there are also sulfa drugs and other types of medications that contain a sulfonamide molecule; both are different from sulfites.

Sulfur is an element that’s essential for life, and it’s found in sulfites, sulfates, and sulfonamides. By itself, sulfur is not responsible for the reactions that people have to sulfites.

What does it mean to have an allergy to sulfites?

Whenever anyone wonders about an allergic reaction, it’s important to discuss the difference between what we allergists think of as a true allergic reaction and an adverse reaction. There’s a wide spectrum of adverse reactions to food, but not all adverse reactions are allergies.

When we talk about allergies, we usually mean a reaction that has a clear immune basis. The classic example of that is a peanut allergy: when a person with an allergy eats even a small fraction of a peanut and gets hives, has trouble breathing, and could have a life-threatening reaction. This is an immediate immune reaction.

Other adverse reactions to foods—across the spectrum—fall into other categories, like having an adverse reaction due to an intolerance based on the pharmacologic property of the food. A good example of this is that for some people, caffeine makes their heart race or makes them feel jittery. I wouldn’t classify this as an allergic reaction; on the spectrum of adverse food reactions, it’s more of an intolerance due to the chemical property of the food. People can also experience toxic reactions from foods. We see that, for example, in food poisoning. And there are other nonimmunologically based adverse food reactions, including gastrointestinal disorders like heartburn or irritable bowel syndrome.

“Most reactions to sulfites are classified as intolerances.”

Most reactions to sulfites are classified as intolerances. The most common reactions with sulfites are asthma exacerbations (trouble breathing and wheezing) and hives. There are also very rare cases of anaphylaxis in response to sulfites. Anaphylaxis is an immediate immune-mediated reaction and falls more into the category of an allergy—but this is very rare.

Keep in mind that every person is different. We see large variability in the amount of something that can trigger an adverse reaction for a patient.

What does the diagnostic process look like?

Unfortunately, there’s not a reliable blood or skin test to diagnose sulfite reactions. However, there are provocation tests, in which you can be challenged with sulfite materials to test whether you have a reaction.

This is primarily a clinical diagnosis, meaning what matters most is the timeline of what happened, as judged by an allergist or a health care professional. When you go to an allergist’s office and you’re worried about an allergic reaction or an adverse food reaction, they’ll ask you very specific and detailed questions. That’s one of the beauties of allergies: What you tell us really does matter, and it’s very important that we listen to you closely and take a good history. It matters exactly what you ate, when you ate it, when your symptoms started, and if you had ever eaten the food before. Those are all questions you can expect to be asked by an allergist or your physician.

How are we exposed to sulfites?

Sulfites can be present in a variety of things, including baked goods, condiments, shrimp, beer, ciders, drink mixes, and certain wines. Some wines have sulfites added as a preservative, and those will usually have a “contains sulfites” disclaimer on the label. Wine generally has more sulfites than beer, and white wine generally has more sulfites than red wine.

Sulfites are also present in dried fruits in high quantities. Since 1986, the FDA has banned them on most fresh fruits and vegetables and in salad bars as well. The FDA requires labeling on any food or beverage with greater than ten parts per million of sulfites, so things that have a significant level of sulfites are hopefully labeled according to the FDA’s regulation.

It always comes down to looking at the ingredients when those are available. It’s important to keep in mind the different names that sulfites can go under. It would be great if they just said, “This contains sulfites,” but oftentimes, the list includes the other names that I mentioned previously, so you need to take a really close look at the ingredient list.

Tips to Avoid Sulfites

For people with sulfite allergies and intolerances, it’s important to check ingredient lists to see if foods contain sulfites. In the absence of a label, like when you’re eating out at a restaurant, it’s best to avoid baked or processed foods, such as pastries, condiments, cocktail mixers, tea concentrates, and juices, or ask the manager to check the ingredient list on the food’s bulk packaging. Here are some other tips:

• All wines, beers, and kombuchas contain natural sulfites that are created during the fermentation process. Some wines have additional sulfites added as preservatives.
• Look for dried fruit that contains only the fruit itself, with no preservatives listed among the ingredients. Check out Prana Snacks.
• Check the labels on condiments, syrups, jams, grain products, and canned foods to determine whether they contain sulfites. Look for the ingredients sulfur dioxide, potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite, sodium sulfite, or anything that ends in “sulfite.”
• Avoid precut or peeled potatoes as they are the only kind of vegetable for which treatment with sulfites is allowed.
• Sulfites are banned in meat; however, ingredients added to meat or seafood may be treated with sulfites. Always ask when buying from a deli counter, or check the label.
• Shrimp is high in sulfites, so it is best to avoid altogether if you have a sensitivity or allergy.

Who is most prone to a sulfite sensitivity?

People who have asthma can have exacerbations that are caused by exposure to sulfites. We think that about 5 percent of patients with asthma are sensitive to sulfites. Patients with severe asthma are more likely to be sensitive to sulfites than patients without severe asthma. You can also have sulfite reactions even if you don’t have asthma, but that is relatively rare.

Meng Chen, MD, is an allergist and immunologist who received her medical degree from the University of California, San Francisco. She is a clinical assistant professor at the Stanford University School of Medicine.

This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The views expressed in this article are the views of the expert and do not necessarily represent the views of goop.