Sulfites are used as preservatives or food enhancers. They can be in various forms, such as:
- Sulfur dioxide, which is not a sulfite, but a closely related chemical oxide
- Potassium bisulphite or potassium metabisulphite
- Sodium bisulphite, sodium metabisulphite or sodium sulfite
Sulfites release sulfur dioxide, which is the active component that helps preserve food and medicines.
Severe allergic reactions (anaphylaxis) are uncommon
Anaphylaxis has been described but it is very rare. Symptoms include flushing, fast heartbeat, wheezing, hives, dizziness, upset stomach and diarrhea, collapse, tingling or difficulty swallowing.
Sensitivity to sulfites is a different condition from sulfonamide antibiotic allergy
Some patients will have allergic reactions to medications that contain sulfonamide or sulfonamide antibiotics. This is a completely different condition than sulphite sensitivity and is addressed in a separate article on the ASCIA website:
People who react to sulfites do not need to avoid sulfates or sulfur
Some medications have a sulfate component (eg, morphine sulfate) and the most common soaps and shampoos contain compounds such as sodium lauryl sulfate; These are non-allergenic and do not cause reactions in sulfite-sensitive individuals. Similarly, elemental sulfur (for example, in horticulture) can cause respiratory irritation by inhalation, but it is generally not a specific problem for people sensitive to sulfite.
The mechanism by which the reactions occur is not clear
- Sulfur dioxide gas (SO2) is an irritant and, therefore, a possible explanation is the contraction of the respiratory tract reflex due to the inhalation of sulfur dioxide gas. This mechanism can explain the rapid onset of symptoms when drinking liquids such as beer or wine, when breathing SO2 gas during the swallowing process.
- Some people with asthma with sulfite have a partial deficiency in the enzyme sulfite oxidase, which helps break down sulfur dioxide.
- Some people (but not many) have positive skin allergy tests for sulfites, which indicates a true allergy (mediated by IgE).
Diagnosis of suspicion of sulfite sensitivity
Most people with sensitivity to sulfites do not have positive allergy tests and there is currently no reliable test for blood or skin allergy to assess sulfite intolerances.
Sometimes it may be important to perform a supervised feeding task with sulfites under medical supervision to confirm or rule out sensitivity.
Foods that may contain sulfites (partial list):
- Alcoholic Beverages (labeling of sulfites in alcoholic beverages is required if the concentration is 10 parts per million or greater.)
- Bakery Items: Breads containing dough conditioners, cookies, crackers, pie and pizza crusts, tortillas, waffles.
Beverages: Beverages containing sugar or corn syrup, dried citrus fruit beverages, canned bottled, and frozen fruit juices.
- Condiments: Horseradish, relishes, pickles, olives, wine vinegar.
- Dairy: Processed cheese foods.
- Dried Foods: Dried herbs and spices, dried fruits, trail mixes.
- Fish and Shellfish: Fresh shrimp and scallops frozen, canned or dried clams, shrimp, lobster, crab, scallops, dried cod.
- Fruits: Fresh grapes, dried fruits (including raisins and prunes and especially pale fruits that have not discolored), canned, bottled and frozen fruit and juices, maraschino cherries, glazed fruit.
- Gelatins, Fillings, Frostings: Fruit fillings, flavored and unflavored gelatin, pectin, jelling agents, canned frostings and frosting mixes.
- Grain Products: Cornstarch, modified food starch, spinach pasta, gravies, hominy, breading, batters, noodle and rice mixes.
- Hard Candies
- Jams and Jellies
- Nuts: Shredded coconut.
- Plant Protein Products: Soy protein products including tofu, textured vegetable protein, infant formula.
Snack Foods: Filled crackers, dried fruit snacks, trail mixes, tortilla chips, potato chips.
- Sugars: Brown, white, powdered and raw sugars.
- Vegetables: Vegetable juices, canned vegetables (including potatoes), pickled vegetables (including cauliflower, peppers, sauerkraut), “fresh cut” potatoes (as delivered to restaurants), frozen vegetables (including french fries and deli potato salad).
Diagnosis and treatment of sulfite allergy
Hypersensitivity to sulfite is usually diagnosed by excluding and reintroducing food. This method involves the elimination of foods that contain sulfite over a period of time. These foods are gradually reintroduced to see the reaction they can trigger.
Sulfite sensitivity is also determined using a food challenge. This involves the ingestion of a very small amount of sulfite while the subject is under observation and close monitoring by an allergist. If no reaction occurs, the amount of sulfite increases slowly until a safe level of exposure is reached. In case of reaction, medications are administered to remedy the symptoms.
A skin bite test is also used to determine sensitivity to sulfites. Here, the allergen is placed on the surface of the skin and a stitch is made in this area. If there is any skin reaction, such as dents, it may indicate sensitivity to sulfite.
The only solution for allergy to sulfites is to avoid the specific allergen, sulfite. People sensitive to sulfite should avoid foods with a high sulfur content, such as dried fruit, beer, wine, and processed foods. To avoid foods that contain sulfite, it is very important to read the labels of the products with care. Ingredients for food labels include potassium bisulfite, sulfur dioxide, sodium bisulfite, potassium metabisulfite, sodium metabisulfite, and sodium sulfite. People with asthma should be extremely cautious about the use of foods that contain sulfite.
Anaphylactic reactions as a result of sulfite absorption will require immediate emergency treatment, including adrenaline injection, followed by other procedures and observation in the hospital. People with a high sensitivity to sulfite need to carry epinephrine with them at all times.