Sulfites have been used for centuries, primarily as food additives to enhance flavor and maintain freshness. But these sulfur-based compounds are also found naturally in foods like fermented beverages and wines. They are also used as preservatives in various medications to extend their shelf life.
Examples of sulfites include :
- Sodium sulfite
- Sodium bisulfite
- Sodium metabisulfite
- Potassium bisulfite
- Potassium metabisulfite
- Sulfur dioxide
Sulfite exposure can cause many side effects in sensitive people, ranging from mild to life threatening. This is how a sulfite allergy is diagnosed and how you can prevent the reaction if you have been diagnosed with this allergy.
The good news is that sulfites generally do not cause problems in people without allergies or asthma , even when consumed in large amounts. However, in 3 to 10% of people with asthma, sulfites are known to increase asthma symptoms, such as wheezing, chest tightness, and coughing. This usually occurs in adults with serious or poorly controlled medical conditions. Numerous well-controlled studies indicate that some asthmatics may have severe asthma symptoms after consuming foods / beverages that contain sulfite or inhaling sulfite fumes or vapors.
Less is known about sulfite-induced hives / swelling and anaphylaxis , although there have been several reports of severe allergic reactions to sulfite-containing foods / beverages. Some of these people even had positive skin tests for sulfites, suggesting allergic antibodies to the preservative.
Other people have experienced severe reactions to sulfite medications, including intravenous and inhaled medications. These reactions included flushing, hives, and decreased lung function due to the medication.
Sulfites do not cause anaphylaxis in people with idiopathic (unknown) anaphylaxis, mastocytosis , mast cell disease (immune), or in people without asthma or atopy.
It is not fully understood how sulfites cause reactions in some people. Some people clearly develop allergic antibodies to sulfites, while others do not. Gases produced from sulfites can cause muscle cramps in the lungs in some asthmatics, or the reaction may be due to the inability of some people to properly metabolize sulfites.
Although there have been several case reports in which people have been diagnosed with a sulfite allergy by skin testing, there are no reliable skin tests for sulfite allergy available commercially. Diagnosis usually involves a history of adverse reactions after consuming foods or medications that contain sulfite.
To confirm the diagnosis, an allergist may administer oral exposure to a patient suspected of being allergic to sulfites. This procedure involves administering increasing amounts of sulfites to a person to swallow while closely monitoring vital and pulmonary signs. A significant decrease in lung function confirms sulfite sensitivity.
This test should only be performed under the direct supervision of a healthcare professional who has been trained and experienced in this procedure.
Why are sulfites added to food?
Sulfites are added to food for a number of reasons. This includes:
- Reduce bacterial spoilage
- Delays the browning of fruits, vegetables and seafood
- Suppression of bacterial growth during wine fermentation.
- Conditioning of the frozen dough for pie and pizza
- Whitening effect for maraschino cherry and ground corn
In the past, sulfites were added to fresh foods in restaurants and supermarkets to prevent them from browning. Rising reactions led the Food and Drug Administration (FDA) to ban the use of sulfites in fresh foods in 1986, especially fresh salads on salad bars.
The FDA now requires that any food product that contains more than 10 parts per million (ppm) of sulfites be listed on the label. This is because foods with less than 10 ppm sulfites do not cause symptoms, even in people who are allergic to sulfites.
Products containing sulfites
There are several products that contain sulfites.
More than 100 ppm sulfites (very high levels, strictly avoided by those with allergies to sulfites)
- Nuts (except black raisins and prunes)
- Bottled lemon juice (thawed )
- Bottled lime juice (thawed)
- Sauerkraut (and its juice)
- Grape juices (white, sparkling white, sparkling pink, sparkling red)
- Pickled cocktail onions
50 to 99.9 ppm sulfites (medium to high sulfite levels; avoidance recommended for people with sulfite allergies)
- Dried potatoes
- Dips / Sauces
- Fruit fillings
- Maraschino cherry
10 to 49.9 ppm sulfites (low to moderate sulfite levels can cause symptoms in people with severe sulfite allergies)
- Fresh shrimp
- Corn syrup
- Pickled peppers
- Pickles / condiments
- Frozen potatoes
- Maple syrup
- Imported jams and jellies
- Fresh mushrooms
- Imported sausages and meats
- Cordials (alcoholics)
- Dehydrated vegetables
- Various cheeses
- A mix of cornbread and muffins.
- Canned food / seafood in jars
- Clam soup
- Avocado / guacamole dip
- Imported fruit juices and soft drinks
- Cider and apple cider vinegar
Less than 10 ppm sulfites (very low sulfite levels are generally safe, even for people with sulfite allergies)
- Malt vinegar
- Canned potatoes
- Dry soup mix
- Drinks without alcohol
- Frozen pie and pizza dough
- Beet sugar
- Fresh fruit salad
- Homemade jams and jellies
- High fructose corn syrup
Sulfites are added to some medications because of their antioxidant properties and to prevent browning (discoloration) of medications. Sulfites are added to injectable epinephrine (such as EpiPen ) to prevent darkening.
However, epinephrine has not been reported to cause adverse reactions in people allergic to sulfites and should not be withdrawn in an allergic emergency. Injectable epinephrine can save the lives of people with sulfite allergies and anaphylaxis.
Some inhaled solutions used to treat asthma contain sulfites, although many asthma medications have removed them for safety reasons. People allergic to sulfites should avoid taking medications that contain sulfites, with the exception of injectable epinephrine. (like EpiPen and Twinject).
Here are some examples of medications that contain sulfites:
Bronchodilator solutions for asthma
- Epinephrine chloride 1: 1000 (epinephrine)
- Broncosol (isoetharine)
- Izuprel (izuprel hydrochloride )
Topical eye drops
- Bluff-10 (sodium sulfacetamide)
- AK-Dex, Ocu-Dex (dexamethasone)
- Pred-Forte (prednisolone acetate)
- Pre-mild (prednisone)
- Adrenaline, Ana-Kit, EpiPen (adrenaline)
- A-Hydrocort, Solu-Cortef (for hydrocortisone injection)
- Amikin (amikacin )
- Aramine (metaraminol)
- Celeston (as betamethasone phosphate)
- Compazine (prochlorperazine)
- Decadron (dexamethasone phosphate )
- Demerol (meperidine)
- Garamycin (gentamicin)
- Isoetharine HCl
- Izuprel (isoproterenol for injection)
- Levofed (norepinephrine)
- Nebcin (tobramycin )
- Novocaine (Novocaine)
- Phenergan (promethazine)
- Solutions for dialysis and total parenteral nutrition
- Thorazine (chlorpromazine)
- Xylocaine with adrenaline (lidocaine with adrenaline )
Prevention and treatment
In general, people with a known or suspected sulfite allergy should avoid foods and medications that contain sulfites. This should be relatively easy to accomplish given the FDA's mandate to label products that contain 10 ppm or more of sulfites.
In restaurants, however, sulfites can be more difficult to avoid. While the FDA's ban on sulfites from fresh fruits and vegetables in restaurants has significantly reduced the risk of accidental ingestion of sulfites, foods that contain sulfites remain unlabeled. Sulfites in potatoes are a big concern. People with sulfite allergies should avoid all potato products when consumed outside the home, with the exception of baked potatoes with intact skin.
If an allergic reaction develops after consuming a product that contains sulfite, that particular reaction should be treated.
For example, while asthma symptoms may require the use of inhaled bronchodilator solutions (those that do not contain sulfites), severe allergic reactions and anaphylaxis may require treatment with injectable epinephrine. For this reason, it is important that people with severe sulfite allergies carry an injectable epinephrine (EpiPen or Twinject) and obtain a Medical Alert bracelet .
Get the word of drug information
Sulfite allergy is rare and occurs mainly in people with severe asthma. If you have asthma, you do not need to avoid foods that contain sulfites, unless you and your healthcare provider suspect you are allergic to sulfite or have been diagnosed with it.
Frequently asked questions
An allergy to sulfites can make asthma symptoms worse. This can range from a mild wheezing to a life-threatening asthma attack. Less common reactions may include hives, angioadema (swelling under the skin), abdominal pain, and diarrhea. In some cases, this can lead to anaphylaxis , a life-threatening allergic reaction.
Sulfite or sulfur dioxide has antimicrobial properties. It prevents the growth of yeast, bacteria and mold by killing microorganisms and preventing the remaining ones from multiplying. It also prevents food from browning by preventing oxidation.