Medically Reviewed by Neha Pathak, MD on March 22, 2021

What Are Blisters?

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They're bubbles that pop up when fluid collects in pockets under the top layer of your skin. They can be filled with pus, blood, or the clear, watery part of your blood called serum. Most are shaped like circles. Depending on the cause, your blister could itch or hurt a lot or a little. They can appear as a single bubble or in clusters.

Friction

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Friction blisters, named for what causes them, are one of the most common kinds. Think back. Have you ever worn a new pair of hiking boots before you broke them in? Or raked the yard without a pair of garden gloves on your hands? Those are the kinds of things that could cause a friction blister on your heel, toe, thumb, or palm.

Cold and Heat

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Go without gloves in winter and you could get blisters from frostbite. Stay out in the summer sun too long and you might get sunburn. The same thing can happen if you handle frozen goods or touch the stove burner. Both cold and heat are described as “blistering” for good reason: Extreme temperatures can hurt your skin. Blisters are a sign of a type of second-degree burn called partial thickness.

Contact Dermatitis

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Rub up against a pesky plant like poison ivy, and you might end up with blisters of another sort. They’re often a symptom of contact dermatitis, which happens when you touch something you’re allergic to. It doesn’t have to be poisonous, though. Some people react to soap, perfume, detergent, fabric, jewelry, latex gloves, or things used to make tools, toys, or other everyday objects.

Atopic Dermatitis

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Also known as eczema, this condition usually shows up as a rash. But with some types, you can also get blisters filled with clear fluid. Dyshidrotic eczema causes these super-itchy blisters on your palms and the soles of your feet. Blisters filled with pus are a sign your eczema has become infected. If you think you may have a skin infection, see your doctor.

Bug Bites

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Insects can take the blame for some itchy blisters. Scabies are tiny mites that drill into your skin, sometimes leaving curved lines of blisters in their tracks. They often attack the hands, feet, wrists, and under the arms. Flea and bedbug bites can cause little blisters, too. The brown recluse spider has an extra-nasty bite that blisters before bursting to form a painful open sore. If that describes your blister, go to the doctor right away.

Chickenpox & Shingles

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Some viruses can cause blisters. The herpes virus is a common culprit. It’s present in chickenpox, a contagious illness that starts with red bumps that become blisters and then scab over. If you’ve had chickenpox, you also can get shingles, which targets nerves and causes a painful rash with blisters. The CDC says people 60 and older should get a one-time vaccination to prevent shingles. It also recommends two doses of chickenpox vaccine for anyone who hasn’t had the disease.

Herpes Simplex

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Fever blisters on your lips, mouth, or genitals are a sign of the herpes simplex virus. The fluid in these sores carries and spreads the virus through sex, or by kissing or sharing utensils. Many people don’t know they have herpes because symptoms are usually mild. If you have fever blisters or you think you've been exposed to herpes, talk to your doctor. There’s no cure, but certain drugs can prevent or shorten outbreaks.

Hand-Foot-and-Mouth Disease

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This disease is named after the blisters it causes on these body parts. The infection mostly hits kids younger than 10. The virus spreads through contact with mucus, saliva, feces, or blisters of someone who’s already sick. The infection starts out with a mild fever, runny nose, and sore throat. But the blisters are the big clue that leads to a diagnosis.

Keep It Clean and Dry

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Some blisters get better on their own. Your skin absorbs the fluid, and the blister flattens and peels off. Until that happens, you can use a donut-shaped piece of moleskin padding or tape to help keep it from breaking open.

Don’t Pop if You Don’t Have To

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Resist the urge to pop a blister unless it’s so large -- bigger than a nickel -- or painful that you can’t get around. If that’s the case, your doctor might decide to puncture it with a sterile needle to let the fluid drain out. Once it’s popped, whether your doctor does it or it breaks on its own, gently wash the area with soap and water and apply antibiotic ointment. Cover it with a bandage to keep it clean during the day, but take the bandage off at night to let it dry.

When to See Your Doctor

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Go to the doctor if you have a fever, chills, or other flu-like symptoms at the same time you have blisters. You could have a virus or an infection. Other symptoms of infection can include: pain, swelling, redness or warmth, red streaks leading away from your blister, or pus coming from it. Blisters around your eyes or on your genitals are also cause for concern.

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