Allergic to Sulfa Drugs? Here Are Some Medications You Can Still Take

Allergic reactions to sulfa drugs can seem intimidating. But if you have a sulfa allergy, millions of people are right there with you. It's estimated that up to 8% of people have had an allergic reaction to a sulfa drug in the past.

Antibiotic medications like Bactrim (sulfamethoxazole / trimethoprim) are some of the most common offenders for sulfa allergies. But there's a frequent misconception about sulfa allergies. It’s often thought that if you’re allergic to one sulfa drug, you’re allergic to all of them. This isn’t always true. If you have a sulfa allergy, there are still certain medications that may be safe for you to take.

Below, we’ll explain what a sulfa allergy is and how to know if you have one. We'll also discuss which medications may still be safe to take if you have a sulfa allergy.

What is a sulfa allergy?

A sulfa allergy is an allergic reaction that happens when your immune system reacts negatively to a sulfa drug. More specifically, when your immune system negatively reacts to the “sulfonamide" portion of a medication. The response can trigger your body to release histamine, which is a natural chemical your body makes when you have an allergic reaction.

Common sulfa allergy symptoms

If you have a sulfa allergy, the specific symptoms you’ll experience can vary. Common symptoms of a sulfa allergy include:

• Skin rashes

• Hives

• Fever

• Itchy skin

• Sensitivity to sunlight

• Swelling of the hands or feet

• Nausea or vomiting

• Diarrhea

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If you experience any symptoms like these after starting a sulfa drug, contact your healthcare provider right away. They’ll help you monitor your symptoms and strategize how to manage them. In many cases, they’ll also tell you to stop taking the sulfa drug.

Serious sulfa allergy symptoms

Some people may develop anaphylaxis after taking a sulfa drug, a rare but potentially life-threatening allergic reaction. Anaphylaxis can occur within minutes to hours of taking a sulfa-containing medication.

Other serious allergic symptoms may include:

• Difficulty breathing or swallowing

• Swelling of throat or tongue

• Irregular heartbeat

• Unusual bleeding

• Blue-colored skin

Separately, there have also been rare reports of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Both of these conditions can cause blisters and peeling of the skin, mouth, or genitals.

If you develop signs or symptoms of anaphylaxis, SJS, or TEN, contact 911 immediately or seek emergency medical attention.

What are sulfa drugs?

Sulfa drugs contain a chemical known as sulfonamide. These often include antibiotics used to prevent and treat bacterial infections. These medications come in formulations such as oral pills or liquids, topical products, and eye drops. One of the most common sulfa antibiotics is Bactrim.

In addition to sulfa antibiotics, some nonantibiotic medications contain sulfonamides too. Top examples at the pharmacy are:

• Celecoxib (Celebrex)

• Sumatriptan (Imitrex)

• Several diuretics, such as furosemide (Lasix) and hydrochlorothiazide (Microzide)

• Certain diabetes medications, such as glyburide (Glynase) and glimepiride (Amaryl)

Sulfa drugs like these can treat several health conditions:

• Seborrheic dermatitis

• Urinary tract infections

• Rosacea

• Wounds

• Eye infections

• Crohn's disease

• Ulcerative colitis

• Rheumatoid arthritis

• Diabetes

• High blood pressure

• Pneumonia

• Leprosy

• Migraines

Should I avoid certain medications if I have a sulfa allergy?

Yes. You should avoid certain medications if you’ve had an allergic reaction in the past to a sulfa drug.

The following sulfonamide antibiotics can cause a reaction if you have a sulfa allergy:

• Bactrim (or Septra, another branded version of sulfamethoxazole / trimethoprim)

• Silver sulfadiazine (Silvadene)

• Sulfacetamide (Bleph-10)

• Sulfadiazine

• Dapsone (Aczone)

Sulfasalazine (Azulfidine) isn’t an antibiotic, but it can also cause a reaction for people with sulfa allergies.

But what if you need a sulfa drug?

If you have a sulfa allergy and need an antibiotic, your healthcare provider will likely give you a non-sulfonamide antibiotic. But there are certain situations where sulfa drugs like Bactrim are still go-to choices — even if you’ve had a minor reaction in the past. One example would be for a certain type of pneumonia prevention in people with weakened immune systems.

In other cases, a sulfa rechallenge or desensitization might be considered. This is especially true if no other medications are good options. A rechallenge involves restarting the sulfa drug that was stopped. Desensitization is a procedure where you’re slowly given the drug in higher amounts until you can tolerate the needed dose.

Both of these procedures are typically done in a clinic or healthcare setting so immediate medical care is available if problems arise.

However, there are other medications you may be able to take. This is due to the chemistry of how they’re made. More on this next.

Sulfa drugs to consider for people with Bactrim allergies

Many people with sulfa allergies can tolerate non-antibiotic sulfonamide medications. Except for sulfasalazine, nonantibiotic sulfonamides show a low risk of evidence of cross-reactivity. This means they shouldn't trigger an allergic reaction if you have an allergy to sulfa antibiotics.

If you've had an allergic reaction to antibiotics like Bactrim, the sulfa-based drugs in the table below are possibilities for you to consider taking.

Important: Before you take any of these medications, make sure to check in with your healthcare provider. They can tell you if these medications are truly safe for you to take.

How to prevent a sulfa allergic reaction

If you’ve had an allergic reaction to a sulfa drug in the past, speak with your healthcare provider about medications you should avoid and medications you can try. They’re your best resource for navigating your options and preventing future reactions.

Some precautions can go a long way for your safety, too:

• Don’t take the medication that you’re allergic to.

• Inform all of your healthcare providers and pharmacies about your allergy and make sure they document it in your medical record.

• Document the medication you're allergic to and the reaction you had on your current medication list.

• Carry an EpiPen (epinephrine) in the case of an emergency, especially if your previous reaction was severe.

• Wear a medical bracelet or carry a medical ID card that states your allergy.

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Written by:

Nidhi Gandhi-Patel, PharmD, BS

Nidhi Gandhi-Patel, PharmD, is a licensed pharmacist in Illinois. She has worked in the pharmacy profession for more than 6 years and currently is the interim Co-Director of the AACP Transformation Center at the American Association of Colleges of Pharmacy (AACP).

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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