Vesicles form when fluid is trapped under the epidermis (top layer of skin). A rash with multiple vesicles is called a vesicular rash.

Sometimes, vesicles merge into a larger single blister (called a bulla). A rash with multiple blisters (bullae) is called a bullous rash. When they burst, the fluid may crystallize and leave behind a crust.

This article looks at nine common causes of blisters and what to do about them.

Chickenpox

Chickenpox is an itchy rash. It’s caused by the varicella virus. The chickenpox vaccine has made it far less common than it used to be.

The classic chickenpox blister looks like a dewdrop. You can have between 100 and 300 of them during a chickenpox infection. They develop all over the body, particularly on the trunk, face, and scalp. They can also appear on the mucous membranes of the throat, eyes, anus, and genitals.

The rash comes on between 10 and 21 days after you’re exposed to the virus. Other symptoms usually start a day or two earlier.

They include:

FeverHeadacheFatigueLoss of appetite

Over the next eight to 12 hours, the fluid-filled blisters get cloudier and burst. That leaves a yellowish crust.

New blisters can form where old ones have healed. They may leave a permanent scar (pockmark).

Shingles

Shingles (herpes zoster) is a painful rash. It’s caused by a reactivation of the chickenpox virus. Early symptoms are fatigue and burning, itching, or aching of the skin.

After an initial chickenpox infection, the virus embeds itself in nerve cells. Years later, the rash can develop along a dermatome (the nerve’s path). Each dermatome provides nerve function to a specific area of skin on one side of your body. So the shingles rash usually appears as a stripe or band across the skin.

Blisters cause persistent and often severe pain when they rupture. They’ll heal in seven to 10 days. A rare complication, postherpetic neuralgia, can cause persistent pain that lasts for weeks, months, or even years.

The vesicle fluid can transmit the virus to others who haven’t had:

ChickenpoxChickenpox vaccine

A person infected by someone who has shingles would develop chickenpox, rather than shingles. This is especially dangerous for young babies or people who have a weak immune system.

Rhus Dermatitis (Poison Ivy)

Rhus dermatitis is caused by contact with an oily chemical called urushiol. It’s found in some plants including:

Poison ivy Poison oak Poison sumac

If you’re sensitive to urushiol (and most people are), the itchy, blistering rash develops anywhere the oils touch your skin. Fluid from the blisters can’t spread the rash to other people. But contact with the oils on your skin or clothing can.

Rhus dermatitis is a form of allergic contact dermatitis. It’s treated with topical steroids. Over-the-counter (OTC) calamine lotion can help relieve symptoms.

The rash heals on its own in about three weeks. It rarely scars.

Genital Herpes

Genital herpes is most often caused by the herpes simplex virus 2 (HSV-2). Symptoms typically start with tingling or burning. Then, herpes blisters develop and erupt into painful ulcers. 

Shingles are a reactivation of the same virus. The blisters are extremely painful when they rupture.

Rhus dermatitis is caused by an oil in poison ivy, poison oak, or poison sumac. It often clears on its own, and you may be given topical steroids to help clear it up.

Blisters can be hard to see in the vagina, and sometimes genital herpes can be misdiagnosed as a bladder or yeast infection.

The fluid in herpes vesicles can transmit the virus during sex or other intimate contact.

Antiviral drugs can shorten an outbreak. But nothing can get HSV-2 out of your body completely.

Cold Sores

Cold sores are also known as fever blisters or oral herpes. They’re usually caused by the herpes simplex virus 1 (HSV-1).

Once you’ve been exposed to HSV-1, the virus stays in your body forever. It reactivates now and then and causes blisters.

The triggers for a cold sore outbreak include:

Chapped lipsStressFatigueExcessive sun exposureFever

A cold sore can be painful. It may take up to two weeks to heal.

Antiviral medications can relieve symptoms and shorten outbreaks. Topical medications are also available.

Dyshidrotic Eczema

Dyshidrotic eczema, or pompholyx, is an itchy rash. It mainly develops on the hands and feet. It isn’t contagious.

You may be more likely to get it if you have atopic dermatitis. The cause is unknown, and it’s believed to be related to abnormal immune function.

The vesicular rash looks almost like tapioca pudding. It can take up to three weeks to heal. It may leave behind red, dry, and cracked scales.

Large, painful blisters can develop. If they’re on your feet, it may be hard to walk. The rash is most often treated with topical steroids.

Scabies

Scabies is a rash caused by tiny mites that burrow into your skin. The red, bumpy rash often has tiny, fluid-filled blisters.

Dyshidrotic eczema is an itchy rash on the hands and feet. It’s treated with topical steroids.

A scabies rash is most often seen on:

WristsBetween the fingersUnder the armAround the waistline

You can transmit scabies through skin-to-skin contact and you can catch it from contaminated clothing and bedding. It usually takes more than a quick hug or handshake, though.

Scabies is commonly treated with anti-parasitic lotions. They kill both the mite and its eggs. Oral medications are also available.

Impetigo

Impetigo is an infection that affects the upper layers of the skin. It can be caused by Streptococcus or Staphylococcus bacteria.

It commonly occurs on the face or limbs. Sores quickly develop into vesicles. Burst blisters leave behind a honey-colored crust.

A less common form of impetigo causes large blisters known as bullae. Newborns and younger children get them most often.

Impetigo treatment usually involves broad-spectrum antibiotics.

ID Reaction

An Id reaction is a secondary eruption related to a distant inflammatory or infectious rash. It is a form of auto-eczematization that develops in response to an infection or inflammation.

Infections linked to Id reaction include:

Athlete’s footRingwormJock itch

Treating the infection should clear up the rash.

Home Remedies for Itching

Different causes of blisters need different treatments. Meanwhile, you may have an annoying itch to deal with.

Common home remedies include:

A fragrance-free, additive-free moisturizerA topical anesthetic that contains pramoxineTopical treatments that contain menthol or calamineAloe vera gelCoconut oilCold compresses or ice packs (use for 5-10 minutes at a time)Oatmeal baths

If your itch is severe or doesn’t respond to these remedies, talk to a healthcare professional.

Summary

Fluid-filled blisters can come from many causes.

Chickenpox, shingles, genital herpes, and cold sores are caused by viruses. Rhus dermatitis comes from an oil in plants like poison ivy.

Dyshidrotic eczema likely comes from impaired immune function. Scabies is caused by burrowing mites.

Impetigo is caused by bacteria. Id reaction often comes from infections in other areas of the body.

There are home remedies that can help relieve the itch while the underlying cause is treated.

A Word From Verywell

If you have blisters, don’t assume they’re harmless and will go away on their own. They might, but they might require treatment.

See a healthcare professional so you know for sure what’s causing the vesicles. Then you can choose the right treatments to clear up your skin.

An allergic reaction to drugs, food, or a skin irritantAn autoimmune disorderA bacterial, fungal, or viral infectionA burnContact with a chemical irritantChemotherapy treatmentEczema Friction (“rug burn”)