A blister, which is also called a vesicle by medical professionals, is a raised portion of skin that is filled with fluid. You’re probably familiar with blisters if you’ve ever worn ill-fitting shoes for too long.

This common cause of blistering produces vesicles when friction between your skin and the shoe results in layers of skin separating and filling with fluid.

Blisters are often annoying, painful, or uncomfortable. But in most cases, they aren’t a symptom of anything serious and will heal without any medical intervention. If you ever have unexplained blistering on your skin, you should see your healthcare provider for a diagnosis.

Blisters can be caused by friction, infection, or, in rare cases, a skin condition. Here are 16 possible causes of blisters.

Warning: Graphic images ahead.

Cold sore

• Red, painful, fluid-filled blister that appears near the mouth and lips
• Affected area will often tingle or burn before the sore is visible
• Outbreaks may also be accompanied by mild, flu-like symptoms such as low fever, body aches, and swollen lymph nodes

Herpes simplex

• These painful blisters occur alone or in clusters and weep clear yellow fluid and then crust over
• Signs also include mild flu-like symptoms such as fever, fatigue, swollen lymph nodes, headache, body aches, and decreased appetite
• Blisters may reoccur in response to stress, mensturation, illness, or sun exposure

Genital herpes

• This sexually transmitted disease (STD) is caused by the HSV-2 and HSV-1 viruses.
• It causes herpetic sores, which are painful blisters (fluid-filled bumps) that can break open and ooze fluid.
• The infected site often starts to itch, or tingle, before the actual appearance of blisters.
• Symptoms include swollen lymph nodes, mild fever, headache, and body aches.

Impetigo

• Common in babies and children
• Rash is often located in the area around the mouth, chin, and nose
• Irritating rash and fluid-filled blisters that pop easily and form a honey-colored crust

Burns

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

• Burn severity is classified by both depth and size
• First-degree burns: minor swelling and dry, red, tender skin that turns white when pressure is applied
• Second-degree burns: very painful, clear, weeping blisters and skin that appears red or has variable, patchy coloration
• Third-degree burns: white or dark brown/tan in color, with leathery appearance and low or no sensitivity to touch

Contact dermatitis

• Appears hours to days after contact with an allergen
• Rash has visible borders and appears where your skin touched the irritating substance
• Skin is itchy, red, scaly, or raw
• Blisters that weep, ooze, or become crusty

Stomatitis

• Stomatitis is a sore or inflammation on the lips or inside of the mouth that can be caused by infection, stress, injury, sensitivity, or other disease.
• The two main forms of stomatitis are herpes stomatitis, also known as a cold sore, and aphthous stomatitis, also known as a canker sore.
• Herpes stomatitis symptoms include fever, body aches, swollen lymph nodes, and painful, fluid-filled blisters on the lips or in the mouth that pop and ulcerate.
• With aphthous stomatitis, ulcers are round or oval with a red, inflamed border and yellow or white center.

Frostbite

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

• Frostbite is caused by extreme cold damage to a body part
• Common locations for frostbite include fingers, toes, nose, ears, cheeks, and chin
• Symptoms include numb, prickly skin that may be white or yellow and feel waxy or hard
• Severe frostbite symptoms include blackening of the skin, complete loss of sensation, and fluid- or blood-filled blisters

Shingles

• Very painful rash that may burn, tingle, or itch, even if there are no blisters present
• Rash comprising clusters of fluid-filled blisters that break easily and weep fluid
• Rash emerges in a linear stripe pattern that appears most commonly on the torso, but may occur on other parts of the body, including the face
• Rash may be accompanied by low fever, chills, headache, or fatigue

Dyshidrotic eczema

• With this skin condition, itchy blisters develop on the soles of the feet or the palms of the hands.
• The cause of this condition is unknown, but it may be related to allergies, like hay fever.
• Itchy skin occurs on the hands or feet.
• Fluid-filled blisters appear on the fingers, toes, hands, or feet.
• Dry, red, scaly skin with deep cracks are other symptoms.

Pemphigoid

• Pemphigoid is a rare autoimmune disorder caused by a malfunction of the immune system that results in skin rashes and blistering on the legs, arms, mucous membranes, and abdomen.
• There are multiple types of pemphigoid that differ based on where and when the blistering occurs.
• A red rash usually develops before the blisters.
• The blisters are thick, large, and filled with fluid that’s usually clear but may contain some blood.
• Skin around the blisters may appear normal, or slightly red or dark.
• Ruptured blisters are usually sensitive and painful.

Pemphigus vulgaris

• Pemphigus vulgaris is a rare autoimmune disease
• It affects the skin and mucous membranes of the mouth, throat, nose, eyes, genitals, anus, and lungs
• Painful, itchy skin blisters appear that break and bleed easily
• Blisters in the mouth and throat may cause pain with swallowing and eating

Allergic eczema

• May resemble a burn
• Often found on hands and forearms
• Skin is itchy, red, scaly, or raw
• Blisters that weep, ooze, or become crusty

Chickenpox

• Clusters of itchy, red, fluid-filled blisters in various stages of healing all over the body
• Rash is accompanied by fever, body aches, sore throat, and loss of appetite
• Remains contagious until all blisters have crusted over

Erysipelas

• This is a bacterial infection in the upper layer of the skin.
• It's usually caused by the group A Streptococcus bacterium.
• Symptoms include fever; chills; generally feeling unwell; a red, swollen, and painful area of skin with a raised edge; blisters on the affected area; and swollen glands.

Dermatitis herpetiformis

• Dermatitis herpetiformis is an itchy, blistering, burning skin rash that occurs on the elbows, knees, scalp, back, and buttocks.
• It's a symptom of autoimmune gluten intolerance and celiac disease.
• Symptoms include extremely itchy bumps that look like pimples filled with clear liquid that form and heal in waxing and waning cycles.
• Symptoms can be controlled by following a gluten-free diet.

Causes of blisters

• Contact dermatitis can also cause blisters. This is a skin reaction to allergens, like poison ivy, latex, adhesives, or irritants like chemicals or pesticides. It can cause red, inflamed skin and blistering.
• Burns, if severe enough, can produce blistering. This includes burns from heat, chemicals, and sunburns.
• Allergic eczema is a skin condition that is caused or worsened by allergens and can produce blisters. Another type of eczema, dyshidrotic eczema, also results in blistering; but its cause is unknown, and it tends to come and go.
• Frostbite is less common, but it can cause blisters on skin that’s exposed to extreme cold for a prolonged period of time.

Blistering can also be a symptom of certain infections, including the following:

• Impetigo, a bacterial infection of the skin that can occur in both children and adults, may cause blisters.
• Chickenpox, an infection caused by a virus, produces itchy spots and often blisters on the skin.
• The same virus that causes chickenpox also causes shingles, or herpes zoster. The virus reappears in some people later in life and produces a skin rash with fluid vesicles that can rupture.
• Herpes and the resulting cold sores can lead to skin blistering.
• Stomatitis is a sore inside the mouth that can be caused by herpes simplex 
• Genital herpes can also result in blisters around the genital region.
• Erysipelas is an infection caused by the Streptococcus group of bacteria, which produces skin blisters as a symptom.

More rarely, blisters are the result of a skin condition. For many of these rare conditions, the cause is unknown. A few skin conditions that cause blisters include:

• porphyrias
• pemphigus
• pemphigoid
• dermatitis herpetiformis
• epidermolysis bullosa

Treatment for blisters

If you know the cause of your blister, you may be able to treat it by covering it with bandages to keep it protected. Eventually the fluids will seep back into the tissue, and the blister will disappear.

You shouldn’t puncture a blister unless it is very painful, as the skin over the fluid protects you from infection. Blisters caused by friction, allergens, and burns are temporary reactions to stimuli. In these cases, the best treatment is to avoid what is causing your skin to blister.

The blisters caused by infections are also temporary, but they may require treatment. If you suspect you have some type of infection, you should see your healthcare provider.

In addition to medication for the infection, your healthcare provider may be able to give you something to treat the symptoms. If there is a known cause for the blisters, such as contact with a certain chemical or use of a drug, discontinue use of that product.

Some conditions that can cause blisters, such as pemphigus, don’t have a cure. Your healthcare provider can prescribe treatments that will help you manage symptoms. This may include steroid creams to relieve skin rashes or antibiotics to cure skin infections.

In most cases, blisters aren’t part of a life-threatening condition. Most will go away without treatment, but may cause you pain and discomfort in the meantime.

The quantity of blisters you have, and whether these have ruptured or have become infected, is important in the outlook of your condition. If you treat an infection that is causing blisters, your outlook is good. For rare skin conditions, how well treatments work will depend on the individual situation.

Prevention of friction blisters

• Always wear comfortable, well-fitting shoes.
• If you will be walking for a long period of time, use thickly cushioned socks to reduce friction.
• As you walk, you may feel a blister beginning to form. Stop and protect this area of skin with a bandage to prevent further friction.