Sulfa Allergy

Sulfa allergy occurs when an individual has an allergic reaction to drugs that contain sulfonamides. Sulfa is a constituent of some antibiotics, which are often used to treat skin disorders, eye infections, and rheumatoid arthritis.

There is a difference between sulfa and sulfite. Sulfites are used as additives and preservatives in wines and certain foods, but both can cause allergic reactions. A person with sulfa allergy will not necessarily allergic to sulfites so there is no cross-reactivity.


  • Rash or hives
  • Itchy skin and eyes
  • Swelling of the mouth or throat
  • Asthma
  • Nausea
  • Abdominal pain

Medications that contain sulfa

Consult your doctor if you think you have sulfa allergy and avoid the following medications:

  • Antibiotic combination drugs, such as trimethoprim-sulfamethoxazole (Septra and Bactrim) and erythromycin-sulfisoxazole
  • Dapsone, a treatment for leprosy, dermatitis, and some types of pneumonia
  • Sulfasalazine (Azulfidine), which is used to treat Crohn’s disease, rheumatoid arthritis, and ulcerative colitis
  • Sulfacetamide (BLEPH-10), or eye drops for eye infections
  • Sulfazidine silver (Silvadene), a cream used for burn infections

Note: Not all medications that contain sulfonamides will cause a reaction in people with sulfa allergy. That’s why it’s important to consult a doctor about certain medications before taking them.

Stevens-Johnson syndrome

This is a rare form of sulfa allergy which affects a person’s skin, mucous membrane, genitals, and eyes. Symptoms include painful red blisters around the mouth, throat, eyes, or genitals, severe red or purple skin rash, sloughing or shedding of skin, fatigue, diarrhea, nausea, and fever.


For hives or itching, doctors may prescribe antihistamines or corticosteriods. If a person experiences respiratory difficulties, he or she may require a bronchodilator to help widen the air passages to and from the lungs. When symptoms of anaphylaxis or Stevens-Johnson syndrome occur, it should be treated as a medical emergency.

Those with Stevens-Johnson syndrome are usually admitted to an intensive care unit for treatment that includes corticosteriods for inflammation, antibiotics to control skin infections, and intravenous immunoglobulins to stop the disease from progressing.

A doctor can determine the best course of action and may recommend an appointment with a specialist to carry out further tests and give advice on which medications and products to avoid.

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