Sulfite Allergy – Cooking Up Trouble

in Other Food Allergy
Published: July 2, 2010

These chemical additives cause reactions that mimic allergy. But the reason why remains a mystery.

Consider the Canadian Food Inspection Agency’s list of the Top 11 food groups that cause the most frequent and severe allergic reactions. Eight of the names will be familiar to most North Americans: peanuts, tree nuts, milk, eggs, fish and shellfish, soy and wheat. (Sesame and mustard are also on Canada’s list.)

But the eleventh name on the list may surprise: sulphites (or sulfites). These are the chemical additives used to stop food from browning or spoiling. In 1 per cent of the population, mostly those with asthma, even tiny amounts of sulfites can cause reactions. An estimated 4 per cent of asthmatics are sensitive to them. In Canada, where they’ve garnered enough attention to make CFIA’s Top 11 list, there have been reports of more than 100 sulfite-related reactions, ranging from nausea and abdominal pain to anaphylactic attacks. At least one Canadian has died.

Although sulfites are known to trigger symptoms in susceptible individuals that appear to be allergic reactions, including anaphylaxis, scientists still don’t know how they do this. Unlike the other food groups on U.S. and Canadian allergen lists, sulfites are chemicals, not proteins. Researchers don’t yet know whether sulfites cause the immune systems of some people to respond abnormally or whether they set off some other mechanism that causes allergic-like reactions. The researchers also haven’t figured out why sulfites pose a threat to some people and not to others.

One theory is that people sensitive to sulfites have a genetic abnormality that hinders the body’s breakdown of these chemicals. However, Dr. Susan Tarlo, a respiratory physician at Toronto’s University Health Network and a specialist in lung disease and allergic response, says her extensive research does not confirm that theory. Another theory links sulfite sensitivity to a lack of B12 vitamins, but that research is still not conclusive.

If you develop hives or have trouble breathing after a restaurant dinner and a glass of wine and suspect you may have this sensitivity, the first step is to see an allergist and confirm what is causing your reaction. The only way to be sure that it is a sulfite sensitivity is to undergo an oral challenge in a hospital setting. In such a test, doctors will give you a glass of juice with sulfites to see whether you respond. (For sulfites, Tarlo says a skin test is not reliable enough.)

The CFIA has added sulfites to its top 11 allergens list because they cause allergic-like reactions in such a significant number of people. (One per cent of the Canadian population equates to about 340,000 individuals.) But there is no scientific evidence that the prevalence of sulfite sensitivity has actually increased over the past years.

According to Tarlo, the incidence may simply be the result of better diagnosis and awareness. In fact, in the United States, studies show that the number of sulfite reactions has actually declined with improved food labeling and a ban on spraying sulfites on raw fruits and vegetables.

Sulfite sensitivity is sometimes discovered in children but is most often identified in adults, perhaps because it is as adults that we begin to drink wine and beer. As most wines ferment, sulfites occur naturally, and winemakers usually add more of the chemicals to prevent spoiling.

Some organic wineries carefully avoid these additional sulfites, and in the United States, several organic wines have been deemed to fall within safe guidelines of under 10 parts per million of the chemicals. (There are a few organic wineries in British Columbia as well.)

But not everyone with the sensitivity has summoned the nerve to try these new vintages. The reactions that Glynnis Brassil gets to sulfites might be clinically described as “mild” when compared to life-threatening food allergies. But don’t tell her that: if she drinks regular wine or eats a food containing sulfites, Brassil develops a migraine so painful that “my hair hurts.” She does not drink wine at all any more and, to avoid headaches that can last a number of days, the Vancouver computer consultant strives to “eat fresh, fresh food, not preserved, prepared or processed.”

Canadian regulations prohibit sulfites from being added or sprayed on fruit and vegetables that are intended to be consumed raw, with a key exception – grapes. But sulfites can be legally added to a wide range of packaged foods, including dried fruit and vegetables, which can have very high levels of sulfites, as well as baked goods, canned vegetables, soup mixes, jams, pickled foods, potato chips, trail mix, molasses, shrimp, guacamole, and maraschino cherries.

In the United States, packaged food with more than 10 parts per million of sulfites must disclose the presence of sulfites on the label. In Canada the rules are a little different: If sulfites are added to food that is sold in packages, the label must say so. If you don’t see sulfites on the label, however, that’s no guarantee because there are many exceptions to the rule. For example, the labeling rule does not apply to the ingredients used in a food, such as glucose, which may include sulfites. It does not apply to food prepared locally and sold in vending machines, or to food cooked and sold in a grocery store.

Sulfites that occur naturally don’t have to be listed. In Canada, wine labels do not have to disclose the presence of sulphites (real or added), although proposed federal rules may change that in the coming years.

Consumers can also be fooled by the names on a food label. The word “sulfites” is not always used. Sometimes the chemical compound is listed instead. Here are the names to watch out for: potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite, sodium sulfite, sodium dithionite, and sulphurous acid. All are sulfites.

There is another mysterious aspect to sulfite sensitivity: It is highly individualistic. Some people can drink a glass of wine. Others will react after a spoonful of sauce that contains a dash of red wine.

This means that each person with a sulfite sensitivity will have to tailor his or her plan of action for dealing with food. If you are sensitive to sulfites, you’ll want to get advice from your allergist and perhaps a dietitian about foods that are safe to eat. There are exceptions to the labeling rules and you need to be aware of foods that may contain this allergen.

Despite shortcomings though, current labels have proved “a huge help,” notes Brassil. “I have to go shopping with my glasses on; I have to read every ingredient on everything.” One of her personal strategies – avoid imported foods where possible, because the ingredients of the listed ingredients are not at all clear.

Staying Safe

  1. If you’re sensitive to sulfites, avoid dried fruit and vegetables.
  2. Most wines produce natural sulfites in the fermentation process, and sulfites are also added as a preservative. But some organic wineries are creating wines with no added sulfites. Some, such as LaRocca Vineyards in California, say their wines also have no natural sulfites or only traces of it. LaRocca’s red wine contains no sulfites, while its white contains only 1 part per million of the chemical.
  3. Check wine labels. Under U.S. rules, wine with less than 10 parts per million of sulfites is considered safe for most who are sensitive, and winemakers are required to list the sulfite content when it is greater than that. If the the wine contains only 8 ppm, the winemaker is allowed to label it: “sulfite-free”. Canada does not require winemakers to disclose the level of sulfites on labels, but the government has proposed legislative changes that would require this. In the meantime, if it’s a North American wine, check with the winery or distributor regarding questions on sulfite content. And don’t leave “sulfite-free” bottles of wine on the shelf for long; they may spoil.
  4. Always read package labels, but be cautious. Even if you don’t see sulfites on the label, they may still be hidden in the food, in one of the ingredients like glucose. Also, remember that some foods prepared in grocery stores or sold in vending machines don’t have to be labelled.