Sulfites are commonly used in the processing and storage of several foods and drinks. They were finally banned for use on produce in 1986. At that time the FDA also required other beverages containing sulfites, such as wine, beer and dried fruit to have warning labels. Sulfites are sulfur-based preservatives that are used to prevent or reduce discoloration of light-colored fruits and vegetables, prevent black spots on shrimp and lobster, inhibit the growth of microorganisms in fermented foods such as wine, condition dough, and maintain the stability and potency of certain medications. Sulfites can also be used to bleach food starches, to prevent rust and scale in boiler water that is used to steam food and even in the production of cellophane for food packaging.

It appears that sulfite sensitivity may be caused by a relative deficiency of the enzyme sulfite oxidase which breaks down sulfites and requires molybdenum as a cofactor. As with lactase deficiency, this is a metabolic problem and not an allergic one. The other proposed mechanisms are a cholinergic reflex response to inhaled sulfur dioxide and IgE mediated delayed hypersensitivity. Yet, no antibody or specific complement activity has been identified in association with sulfite exposure. However, asthmatics seem to be more prone to develop bronchospasm when challenged with sulfur dioxide.

Asthma, nasal and sinus congestion, rhinitis, postnasal drip, frontal headache and bronchospasm can be triggered by sulfites. Sulfites can be measured in the urine, and used as a means of monitoring symptom correlation with treatments such as molybdenum. The FDA estimates that 1% of people are sulfite-sensitive and 5% of those also suffer from asthma. A person can develop sulfite sensitivity at any point in life.

Products That Contain Sulfites
Sulfites can occur naturally in foods or are added to enhance food products. Sulfites are made naturally during the fermentation of wine. There is a variety of foods that contain sulfites including baked goods, soup mixes, jams, canned and dehydrated vegetables, pickled foods like sauerkraut and pickles, gravies, dried fruit, potato chips, trail mix, beer, wine, vegetable juices, bottled lemon juice, bottled lime juice, tea, condiments, molasses, fresh or frozen shrimp, guacamole (avocados), maraschino cherries, and dehydrated, pre-cut, or peeled potatoes. The list also includes lettuce, mushrooms, grapes, relishes, shredded coconut, peppers, onions, grape juice and gravies.

There are six names used for sulfites: sulfur dioxide, sodium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, and potassium metabisulfite. Sulfites, bisulfites and metabisulfites are all dry chemical forms of the gas, sulfur dioxide.

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