How Do I Know if My Blister Is Infected? Plus, How to Treat It

Here’s how to identify an infected blister, what to do about it, and when to seek medical attention.

Watch for these telltale signs of an infected blister.

What an Infected Blister Looks Like

Signs and Symptoms of an Infected Blister

• Heat, swelling, redness, and pain around the blister
• Pus leaking or oozing from the blister
• Red streaks leading from the blister

A fever is a sign that the infection has become severe. “If you experience fevers, chills, or sweats, it’s best to go to the emergency room or urgent care,” says Caren Campbell, MD, a board-certified dermatologist in private practice in San Francisco.

If a blister appears infected, clean it gently with antibacterial soap and water. Then apply an over-the-counter (OTC) hypochlorous acid (HOCI) spray, which is an antimicrobial skin-care product that contains a substance made by the body’s white blood cells to help further disinfect the area. Pat the area dry with a clean towel, recommends Kseniya Kobets, MD, a board-certified dermatologist at Montefiore Einstein Advanced Care Westchester in Elmsford, New York. Finally, apply an OTC bacitracin ointment (used to prevent skin infections) to the blister and cover loosely with a bandage, suggests Dr. Kobets.

If the infection appears worse the following day, call your primary care physician or dermatologist to request an urgent appointment, says Lauren Ploch, MD, a board-certified dermatologist in private practice in Augusta, Georgia. “If they are unable to grant that request, a visit to urgent care may be needed,” she says.

“If the blister is the result of an infection, the fluid can potentially spread the infectious agent to other areas of the skin,” Dr. Ploch says. This is why you should keep a blister cleaned and covered if you suspect it to be infected. Additionally, avoid sharing hygiene items like towels and soap with other people, as doing so can also spread an infection, Dr. Campbell says.

If your symptoms worsen the day after cleaning and covering the blister, visit your primary care provider or dermatologist for treatment as soon as possible.

When you visit a healthcare professional, your doctor will evaluate the blister. “In my office, I culture blister fluid and send it off to the lab to see if there’s bacteria present,” Ploch says. Once your doctor has determined if there’s bacteria in the blister — and what type of bacteria (or virus) — he or she can recommend the appropriate treatment.

Here are some treatments your doctor might prescribe for an infected blister.

• Topical antibiotics are often prescribed for mild blister infections, Ploch says. This may include blisters caused by an infection, such as impetigo, which can be treated with prescription antibiotic ointment for 5 to 10 days.

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• Oral antibiotics may be prescribed if there are multiple infectious blisters, such as impetigo. Or, if you’ve developed a widespread infection, such as cellulitis.

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  The duration of treatment is 3 to 14 days, depending on the infection and size of the infected area, Ploch says.
• Oral antivirals are usually needed for viral blisters, such as cold sores, Ploch says. While cold sores typically resolve on their own in one to two weeks, a prescription oral antiviral medicine may hasten the process.

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   Valacyclovir, an oral antiviral often used to treat cold sores, is typically taken once every 12 hours for one day.

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If you are immunocompromised (because of an autoimmune disease like HIV, AIDS, lupus, or rheumatoid arthritis, or because you're on certain types of cancer treatments), your doctor may still prescribe antibiotics for an infected blister, Ploch says.

• Blisters (fluid-filled bubbles) on the skin typically resolve on their own. But a blister that becomes infected may require medical treatment.
• Signs of an infected blister include heat, swelling, redness, or pain around the blister, pus leaking from the blister, and red streaks leading from the blister.
• If you suspect a blister is infected, wash the area and apply an antibacterial ointment before covering with a bandage.
• Call your doctor if the infection worsens; fevers, chills, or sweats are a sign to visit the emergency room or urgent care.