A gas formed during the digestion of certain commercially prepared foods can set off asthma attacks. Sulfites, used to slow spoilage of fresh foods and improve the appearance of certain processed foods, are a particular problem and have been associated with severe but rarely fatal asthma attacks.

Strictly speaking, sensitivity to sulfites is not an allergy. Small amounts of sulfur dioxide gas may be formed as sulfites enter your stomach, and you may inhale small quantities of this gas fume. Exposure to this irritant gas after eating foods with sulfites can trigger an asthma attack in some asthmatic patients.

The U.S. Food and Drug Administration (FDA) now bans the use of sulfating agents to prevent browning of such foods as salad greens, peeled fruits, fresh potatoes and guacamole. The FDA also requires that all foods and wines containing sulfite levels above 10 parts per million be labeled accordingly. When checking labels for sulfites, look for the words sulfur dioxide, sodium and potassium metabisulfite, sodium and potassium bisulfite and sodium sulfite.

Among the foods and beverages that may contain sulfites are:

• Baked goods (cookies, crackers, pie and pizza crusts, flour tortillas)
• Condiments
• Relishes
• Pickles
• Salad dressing mixes
• Canned and dehydrated vegetables
• Processed fruit (canned, dried, bottled, glazed or frozen)
• Jams and jellies
• Gravy
• Potatoes (frozen, dehydrated, pre-cut)
• Molasses
• Shrimp (fresh, frozen, canned and dried)
• Processed seafood products (canned clams, dried cod, frozen lobster, scallops)
• Products containing sugar derived from sugar beets
• Soup mixes
• Beverages:
• Beer
• Wine and wine coolers
• Hard cider
• Cocktail mixes
• Fruit and vegetable juices
• Bottled lemon and lime juice
• Tea
• "Filled" milk (milk enriched in fat content with vegetable oil)