What are Sulfites?Sulfites or sulfate agents (in the forms of sodium sulfite, sodium bisulfite, sodium metabisulfite, potassium bisulfite and potassium metabisulfite) are common preservatives used in various foods and medications. Sulfites have been used for centuries, mainly as food additives, but can also occur naturally in foods such as fermented beverages and wines.
What is Sulfite Allergy?Sulfites cause little to no problems in most people without allergies and asthma, even when large amounts are consumed.
Sulfites are known to increase asthma symptoms in approximately 5% of asthmatics, particularly in adults with severe disease. Numerous well-controlled studies show that some asthmatics can have severe asthma symptoms with eating sulfite-containing foods/beverages or inhaling sulfite fumes or vapors.
Less is known about hives/swelling and anaphylaxis as a result of sulfites, although various cases have been described in which the consumption of sulfite-containing foods/beverages leads to severe allergic reactions. Some of these people even had positive skin tests to sulfites, suggesting the presence of allergic antibodies to the preservative.
Other people have experienced severe reactions from sulfite-containing medications, including intravenous drugs and inhaled medications. These reactions included flushing, hives and a drop in lung function as a result of the medications being given.
Sulfites do not appear to be a culprit in people suffering from repeated episodes of anaphylaxis of unknown cause, are not a risk for anaphylaxis in people with mastocytosis, and appear to present little to no risk for people without asthma and without atopy.
It’s not completely known how sulfites cause reactions in certain people. Some people clearly make allergic antibodies against sulfites, while others do not. The gases generated from sulfites might cause muscle spasms in the lungs of some asthmatics, or could be related to the inability in some people to metabolize the sulfites appropriately.
How is Sulfite Allergy Diagnosed?While there have been some case reports of people being diagnosed with sulfite allergy using skin testing, there is no reliable, commercially available skin test for sulfite allergy. Typically, the diagnosis is suggested by a history of adverse reactions after consuming sulfite-containing foods or medications.
However, in order for the diagnosis to be confirmed, an allergist may perform an oral metabisulfite challenge for a patient suspected of having sulfite allergy. This procedure involves giving a person increasing amounts of sulfites to swallow, with close monitoring of lung function and vital signs. A significant drop in lung function confirms sensitivity to sulfites. This test should only be performed under direct supervision of a physician who has been trained and is experienced with such a procedure.
Why are Sulfites Added to Foods?Sulfites are added to foods for various reasons. These include:
- Reduction of spoilage by bacteria
- Slows the browning of fruit, vegetables and seafood
- Inhibits of growth of bacteria during fermentation of wines
- Conditioning of dough in frozen pie and pizza crust
- Bleaching effect for maraschino cherries and hominy
In the past, sulfites were added to fresh foods in restaurants and grocery stores to prevent browning. An increase in reactions led the Food and Drug Administration (FDA) to ban the use of sulfites in fresh foods in 1986, particularly on fresh lettuce in salad bars. The FDA now requires that any food containing more than 10 parts per million (ppm) concentration of sulfites to be declared on the label. Foods that contain less than 10 ppm of sulfites have not been shown to cause symptoms, even in people allergic to sulfites.
Which Foods Contain Sulfites?Greater than 100 ppm of sulfites (very high levels, strict avoidance advised in people with sulfite allergy)
- dried fruits (excluding dark raisins and prunes)
- bottled lemon juice (non-frozen)
- bottled lime juice (non-frozen)
- sauerkraut (and its juice)
- grape juices (white, white sparkling, pink sparkling, red sparkling)
- pickled cocktail onions
Between 50 and 99.9 ppm of sulfites (moderate to high levels of sulfite, avoidance advised in people with sulfite allergy)
- dried potatoes
- wine vinegar
- fruit toppings
- Maraschino cherries
Between 10 and 49.9 ppm of sulfites (low to moderate levels of sulfite, may cause symptoms in people with severe sulfite allergy)
- fresh shrimp
- corn syrup
- pickled peppers
- corn starch
- frozen potatoes
- maple syrup
- imported jams and jellies
- fresh mushrooms
- imported sausages and meats
- cordials (alcoholic)
- dehydrated vegetables
- various cheeses
- corn bread/muffin mix
- canned/jarred clams
- clam chowder
- avocado dip/guacamole
- imported fruit juices and soft drinks
- ciders and cider vinegars
Less than 10 ppm of sulfites (very low sulfite levels, generally do not pose a risk, even for people with sulfite allergy)
- malt vinegar
- canned potatoes
- dry soup mix
- soft drinks
- frozen pizza and pie dough
- beet sugar
- fresh fruit salad
- domestic jams and jellies
- high fructose corn syrup
Why are Sulfites Added to Medications?Sulfites are added to some medications for their antioxidant properties as well as the prevention of browning of medications. Sulfites are added to injectable epinephrine (such as in the Epi-Pen) to prevent browning, which decreases the effectiveness of the drug. However, epinephrine has not been reported to cause adverse reactions in people with sulfite allergy, and should not be withheld in an allergic emergency. Injectable epinephrine may prove life saving in people with sulfite allergy experiencing anaphylaxis.
Some inhaler solutions used to treat asthma contain sulfites, although many asthma drugs have had sulfites removed due to safety concerns. People with sulfite allergy should avoid medications containing sulfites, with the exception of injectable epinephrine (Epi-Pen and Twinject).
You've only heard half the story! Don't miss the list of medications that contain sulfites, as well as treatment for sulfite allergy -- all this and more on page 2!!