Sulfa drugs can cause allergic reactions in some people, including hives, swelling and difficulty breathing. If you've ever experienced a reaction to a sulfa drug, your doctor may have diagnosed you with a sulfa allergy. Inform other treating physicians of this allergy and your medical chart will be flagged with this information. If you're ever hospitalized, you may wear a bracelet that informs hospital personnel that you have a sulfa allergy. But sulfa drugs and foods that contain sulfites or sulfates aren't chemically related, so you don't have to worry about sulfa in your diet.
Antibiotics such as Co-Trimoxazole, sold under the brand name Septrin; Sulfamethoxazole, brand-name Gantanol; and Trimethoprim-Sulfamethoxazole, brand name Bactrim; are classed as sulfonamides. These drugs may be used to treat bacterial infections of the digestive or reproductive tracts. They're effective for many people, but some people develop an immune system response to sulfonamides that produces an allergic reaction. The sufonamide bonds to human protein, producing large molecules that can cause you to break out in hives, or swelling of the lips and other mucous membranes, or even difficulty breathing.
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Sulfa vs. Sulfites
Sulfonamides are not the same as sulfites such as sulfur dioxide or sulfate salts. These chemical compounds are sometimes used to preserve foods. Your body metabolizes sulfites and sulfates differently than it does sulfa drugs. Being allergic to sulfa drugs doesn't predispose you to a sulfite allergy and vice-versa. Your body conversts the sulfa compounds used as food preservatives to sulfur dioxide. People with asthma are particularly susceptible to bronchospasms when they're exposed to these preservatives.
Sulfa and Food
Sulfonamides are used in medications, not foods. If you have a sulfa allergy, you don't have to avoid any particular foods. Though some people with sulfa allergies may also be sensitive to sulfites in food, the two allergies are not related. Inform your doctor and your pharmacist if you've been previously diagnosed with a sulfa allergy. If you experience a reaction such as this after taking any antibiotic or other medication, contact your doctor immediately and seek emergency help.
Sulfites and Food
Common foods that may be treated with sulfites include fresh and frozen shellfish such as shrimp and crab, wine, lettuce and other packaged salad greens, dried fruit, maraschino cherries, pickles, saurkraut, lemon, lime or grape juice. Look for ingredients on packages such as sodium sulfite and sodium bisulfite. Inform your doctor if you experience any allergic reaction after eating a food with these ingredients.
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.