Tight shoes aren’t the only cause of blisters. Discover 13 medical conditions that can cause them, from chickenpox to infections and rare autoimmune diseases.

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Blisters (vesicles) are raised parts of skin filled with fluid, often caused by ill-fitting shoes.

Most are annoying and painful but will heal without treatment. However, unexplained blistering should be evaluated by a doctor for another underlying cause.

Read on for 13 other possible causes of blisters.

Warning: Graphic images ahead.

1. Herpes simplex

The herpes virus causes painful blisters that occur alone or in clusters, weep clear yellow fluid, and then crust over. On the mouth, it is known as a cold sore. On the genitals, it is known as genital herpes and is a sexually transmitted infection (STI).

Most often, the viruses HSV-1 and HSV-2 cause oral and genital lesions, respectively. Less commonly, HSV-1 can also cause genital herpes.

The blisters may be triggered by stress, menstruation, illness, or sun exposure. The infected site often starts to itch or tingle before the actual appearance of blisters.

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Learn more about cold sores and genital herpes.

2. Impetigo

Impetigo is a common bacterial infection in babies and children. It causes an irritating rash and fluid-filled blisters that pop easily and form a honey-colored crust.

The rash is often located in the area around the mouth, chin, and nose.

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Read more about impetigo.

3. Burns

This condition is considered a medical emergency. Urgent care may be required.

Burn severity is classified by depth and size: first-degree, second-degree, and third-degree. The blisters will usually form if it is a second-degree burn.

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Read more about burns.

4. Contact dermatitis

Contact dermatitis appears hours to days after an area of skin has been in contact with an allergen or irritant.

The skin becomes itchy, red, scaly, or raw. Blisters can form, which weep, ooze, or become crusty.

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Read more about contact dermatitis.

5. Aphthous stomatitis

Aphthous stomatitis is also known as a canker sore. it can be triggered by an infection, injury, stress, and other diseases.

The ulcers are round or oval with a red, inflamed border and yellow or white center.

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6. Frostbite

This condition is considered a medical emergency. Urgent care may be required.

Frostbite is caused by extreme cold and can affect fingers, toes, nose, ears, cheeks, or chin.

The symptoms include numbness and discoloration of the skin, along with blisters filled with fluid or blood in severe cases.

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Read more about frostbite.

7. Shingles

Shingles is caused by the varicella-zoster virus, which also causes chickenpox.

It’s a very painful rash of fluid-filled blisters, typically appearing in a linear stripe pattern on one side of the body, often accompanied by low fever, chills, headache, or fatigue.

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Read more about shingles.

8. Chickenpox

In chickenpox, clusters of itchy, red, fluid-filled blisters in various stages of healing all over the body.

The rash is accompanied by fever, body aches, sore throat, and loss of appetite. Chickenpox remains contagious until all blisters have crusted over.

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Read more about chickenpox.

9. Dyshidrotic eczema

Dyshidrotic eczema is a condition that causes itchy blisters to form, often on the hands or feet.

The cause is unknown, but it may be related to allergies. Symptoms include dry, red, scaly skin and deep cracks.

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10. Pemphigoid

Pemphigoid is a rare autoimmune disorder causing a skin rash and blisters on various parts of the body.

There are various types of pemphigoid that are based on where and when the blistering occurs.

A red rash is often the first sign of pemphigoid. Later thick and large blisters form, containing clear fluid or blood. If they burst, they typically hurt.

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Read more about pemphigoid.

11. Pemphigus vulgaris

Pemphigus vulgaris is a rare autoimmune disease that affects the skin and mucous membranes of various parts of the body, including the face, genitals, and even the lungs.

It causes painful, itchy blisters that break and bleed easily and can cause pain when eating or swallowing.

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Read more about pemphigus vulgaris.

12. Erysipelas

Erysipelas is a bacterial infection in the upper layer of the skin.

It’s usually caused by the group A Streptococcus bacterium (GAS). Symptoms can include fever and chills, swelling on the skin, and blisters on the affected area.

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Read more about erysipelas.

13. Dermatitis herpetiformis

Dermatitis herpetiformis is an itchy, blistering, burning skin rash that’s associated with celiac disease.

The symptoms include extremely itchy bumps filled with clear liquid that form and heal in waxing and waning cycles.

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Read more about dermatitis herpetiformis.

Most blisters require no treatment. If you leave them alone, they’ll disappear, and the top skin layers prevent infection. You can cover a skin lesion if it’s contagious, such as shingles, when there are active lesions.

Don’t puncture a blister unless it’s very painful, as the skin over the fluid protects you from infection. If the cause is friction, chemicals, or allergens, the best treatment is to avoid what’s causing your skin to blister.

Blisters caused by infections should be evaluated by a doctor. In addition to medication for the infection, they may be able to give you something to treat the symptoms.

Some conditions that can cause blisters, such as pemphigus vulgaris, don’t have a cure and can only be managed with medications. This may include steroid creams to relieve skin rashes or antibiotics to cure skin infections.

For the most common blisters — those caused by friction on the skin of your feet — you can make changes such as wearing well-fitting shoes and thickly cushioned socks. Have a bandage on hand in case they start to form.

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