What’s It Like to Have an Allergic Reaction to Bactrim? 3 People Share Their Experiences

One thing to know about antibiotics is that they can contain chemicals called sulfites, which some people are allergic to.

This is something to keep in mind when taking antibiotics like Bactrim, the brand name for a commonly prescribed antibiotic that contains trimethoprim and sulfamethoxazole. Sulfa medications like this can trigger anaphylaxis, a severe, potentially life-threatening allergic reaction in some people.

Bactrim is used to treat things like urinary tract infections (UTIs) and skin infections. But about 8% of people are allergic to it. The reaction is caused by a sulfite allergy. It can cause a rash or fever in some people and more serious symptoms — including anaphylaxis — in others.

Here’s how three people describe having an allergic reaction to Bactrim.

A frightening experience

Marina Albertson Abell, a project coordinator from Odenton, Maryland, found out the hard way that she is allergic to Bactrim when her doctor prescribed it for a UTI.

She recalls it being a frightening experience. 

“I had an extreme reaction. I experienced vomiting, extreme swelling, and muscle pain. I became violently ill and spent an evening in the ER,” Marina says. 

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“My lips, hands, and feet swelled up, the muscles in my legs became weak, and I was vomiting a lot.”

She stopped taking Bactrim and was prescribed a different antibiotic to treat her infection. She says she was ill for 2 weeks after her allergic reaction. 

“It was awful,” she says.

JoAnn Suchinsky Kay, a 49-year-old clinical social worker from Arnold, Maryland, experienced something similar.

She was also taking Bactrim for a UTI. She was visiting friends in New York at the time. The medication was effective in treating her infection, but it became clear within days that she was also severely allergic to it. 

“My throat and tongue swelled significantly,” JoAnn says. “I was in extreme pain. I’ve never experienced anything like it. I was advised I had a severe allergic reaction to sulfa and that I should no longer take sulfa-based drugs.”

JoAnn has since learned that her 15-year-old daughter has a similar allergy.

A swollen face and hives 

It took more than a week for Lauren McAdams, a 37-year-old stay-at-home mom in Crownsville, Maryland, to realize that she was allergic to Bactrim.

She started taking it for a sinus infection that had not responded to a prior course of antibiotics.

“My doctor decided to try Bactrim since the bacteria appeared to be resistant,” she says.

“On day 8 of a 10-day course of treatment, I woke up with a slightly swollen face and pinpoint-sized hives on my legs,” she says. “I went to urgent care, with the suspicion that it was an allergic reaction, but urgent care was not open yet. I was feeling strange, so I decided to go to the emergency room.”

There, her care team confirmed her suspicion. She had a sulfa allergy. They gave her antihistamines to treat her symptoms.

The next morning, however, Lauren recalls waking up with large hives covering her body, including the bottoms of her feet. 

“Every time I would try to stand, I would inadvertently pass out,” she says.

Her husband took her back to the hospital, and she was admitted for four days. She ended up being diagnosed with Stevens-Johnson syndrome, a rare but serious skin condition that can be triggered by Bactrim.

Though the Bactrim did successfully treat Lauren’s sinus infection, she now knows to steer clear of medications that contain sulfa.

What does the doctor say?

Patricia Pinto-Garcia, MD, MPH 

Medical Editor

Anaphylaxis is a life-threatening condition and it’s often triggered by medications. On TV or in movies, anaphylaxis is often shown as a dramatic event where people are gasping for air as their face swells. That definitely happens to some people, but anaphylaxis symptoms are often more subdued. That doesn’t mean the reaction itself is any less serious, though. 

Sulfa medications are a well-known trigger for anaphylaxis and for other serious non-allergic reactions, such as Stevens-Johnson syndrome. If you’re prescribed Bactrim and you’ve never taken a medication containing sulfa before, pay close attention to your body. Anaphylaxis symptoms start suddenly, but it may take a few doses before your body develops an allergic reaction. 

If you develop symptoms of anaphylaxis, get yourself to an emergency room immediately. Some people get hives along with one or more other symptoms, some of which are mild, like light-headedness or dizziness. Other people get two seemingly unrelated symptoms, like an itchy tongue and vomiting. Keep in mind that not everyone gets hives when they have an allergic reaction.

If you’ve had an allergic reaction to Bactrim, make sure to let all your healthcare providers know about your sulfa allergy. You’ll need to avoid all sulfa-containing medications, not just Bactrim. You can even consider getting a medical alert bracelet that lets first responders and healthcare providers know you have a sulfa allergy in case of an emergency. 

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Written by:

Jillian Amodio

Jillian Amodio is a writer, author, speaker, mental health advocate, and mother of two. She is working on her master’s degree in social work.

Edited by:

Tanya Bricking Leach

Tanya Bricking Leach is an award-winning journalist who has worked in both breaking news and hospital communications. She has been a writer and editor for more than 20 years.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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