Sulfites

Sulfites are sulfur-based preservatives (sulfur dioxide, sodium metabisulfite, potassium metabisulfite, sodium sulfite) used to prevent browning, inhibit bacterial growth, and extend shelf life. They're common in wine, beer, dried fruit (especially light-colored — apricots, golden raisins), packaged potatoes, frozen shrimp and lobster, pickled foods, some baked goods, and many processed foods. They also occur naturally at low levels in fermented foods.

For most people sulfites are well tolerated. But for sulfite-sensitive individuals — especially those with asthma — they can trigger severe reactions: bronchospasm (sudden airway narrowing), wheezing, hives, flushing, anaphylaxis-like reactions. Sulfite sensitivity is most common and severe in people with steroid-dependent asthma, where it may affect ~5–10%.

Asthma and sulfite reactions

In the 1980s, sulfite-related reactions caused several deaths, particularly from sulfite-sprayed lettuce at salad bars. The FDA responded in 1986 by banning sulfite use on fresh fruits and vegetables intended to be eaten raw, and requiring sulfites to be declared on labels when present above 10 ppm. Wine is a common high-sulfite source — "contains sulfites" on the label reflects this. People with confirmed sulfite-asthma reactions need to carry epinephrine and check labels carefully.

Common sources

Highest sulfite content: dried apricots, light-colored raisins, conventional wine, beer, cider, packaged dried potato products, processed shrimp. Moderate: pickled foods, some baked goods, canned vegetables, processed meat. The "natural" or "low-sulfite" wine market is a real thing — some producers use minimal added sulfites, though all fermentation produces some endogenously. Read labels on dried fruit (sulfite-free options are available), and ask before ordering shrimp at restaurants if you've reacted before.