Sulfa Allergies: What You Need to Know

Sulfa drugs can treat a range of health problems from eye infections to rheumatoid arthritis (RA). But if you get a rash or more serious reaction when you take one of these drugs, you may have a sulfa allergy.

Sulfa drugs, also called sulfonamides, include antibiotics and other types of drugs. Allergies happen most often with antibiotics. Around 3% of people have some type of reaction to them.

Tell your doctor right away if you think you’re having a reaction to a sulfa drug. She’ll decide whether to take you off the drug and how to treat your symptoms.

Types of Allergic Reactions

If you’re allergic to sulfa drugs, or any other medication, you may have one or more of these symptoms:

The reaction can also cause these serious skin reactions:

  • Sulfonamide drug hypersensitivity syndrome: Rash, fever, and organ problems begin within 1 to 2 weeks after you start the drug.
  • Drug eruption: Red or swollen, rounded patches form in 30 minutes to 8 hours.
  • Stevens Johnson syndrome: This potentially life-threatening reaction causes skin to blister and peel off.

Other reactions to sulfa drugs include headache, trouble sleeping, cloudy urine (crystalluria), and low blood counts. Rarely, a severe allergic reaction called anaphylaxis happens.

Drugs to Avoid With Sulfa Allergies

Sulfa antibiotics have been widely used for more than 70 years. In fact, the first antibiotic was a sulfa drug introduced in 1936. Today, these drugs include burn creams, vaginal suppositories, and eye drops as well as medications for many types of infections. If you’ve had an allergic reaction to one sulfa antibiotic, you’re probably allergic to all of them.

Here are a few examples of common sulfa drugs that could cause problems:

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Some Sulfa Drugs May Be OK

Even if you’re allergic to antibiotics that have sulfa, you might be able to take some other types of sulfa drugs without a reaction. Ones that may be safe to take include:

But be sure to tell your doctor if you have a sulfa allergy before taking any of these.

Sulfa vs. Sulfite Allergy

A sulfa allergy sounds like a sulfite allergy, but they’re very different. Sulfa drugs treat health conditions. Sulfites are preservatives used in many foods, drinks (especially wine), and medications.

Sulfites can trigger asthma symptoms and on rare occasions can cause anaphylaxis. It’s common for people who have asthma to be sensitive to sulfites. But it’s unusual for other people.

Sulfa drugs and sulfites are not related. Neither are their allergies. There’s no need to give up dried fruit, wine, or other items that contain sulfites if you’re sensitive to sulfa drugs.

WebMD Medical Reference Reviewed by Neha Pathak, MD on January 23, 2017

Sources

SOURCES:

DermNet New Zealand: “Sulfa Drugs and the Skin.”

Canadian Family Physician:“Approach to Managing Patients with Sulfa Allergy.”

American College of Allergy, Asthma and Immunology: “Drug Allergies.”

Merck Manual, Professional Version: “Sulfonamides.”

Cleveland Clinic: “Sulfite Sensitivity.”

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