What Are Blisters?

Blisters (also called vesicles) are bubbles of liquid that develop between layers of skin. They can be painful, especially if they're on a part of your body that experiences repeated friction, like feet and hands.

This article explains the types, causes, symptoms, and treatment of skin blisters.

Types of Blisters

There are several types of blisters, each is caused in different ways. 

Blood Blisters

Blood blisters, as the name suggests, are blisters in which the sac is filled with blood. These may at first appear as red, raised bumps. Over time, the color will darken to a deep purple. These types of blisters can be painful and itchy.

Blood blisters are the result of something pinching your skin.

As such, they commonly occur on parts of your body that are most likely to experience pinching or friction, including your:

• Hands
• Feet
• Mouth

Athletes, dancers, and people who do manual labor are most at risk of developing blood blisters. 

Friction Blisters

Friction blisters are caused by repeated rubbing against the skin. These blisters are filled with clear liquid rather than blood.

You can get a friction blister on your foot from a shoe that doesn’t fit well or on your hand after raking leaves or gardening. 

These types of blisters can occur anywhere on the body that experiences repeated friction. However, they most often occur on the hands and feet.

Heat Blisters

Burns and sunburns cause heat blisters. They may also occur when your skin warms up after frostbite (freezing of the skin and underlying tissues).

Blistering occurs as a result of second-degree burns. These burns affect the epidermis (outer layer of skin) and the dermis (middle layer of skin). Like friction blisters, they are filled with clear liquid.

Since these blisters are associated with severe burns, they can be painful. Blisters as a result of burns can occur anywhere on the body.

Health Conditions

In addition to injuries, blisters can accompany certain diseases, infections, and rashes. Viruses, bacteria, allergies, and irritants cause these types of blisters. For instance:

• Viruses like chicken pox, shingles, and herpes
• Bacterial infections such as impetigo
• Fungal infections like athlete's foot, ringworm, or jock itch
• Parasites like those that cause scabies
• Allergic reactions such as responses to poison ivy
• Eczema (atopic dermatitis)
• Venous insufficiency and swelling in the legs (when vein valves aren't functioning properly)

Blister Symptoms

Blisters may appear after an injury to the skin, such as pinching, friction, or a burn. They might also pop up because of infection.

Regardless, symptoms are generally the same: raised bumps filled with fluid. Depending on the type of blister, the fluid may be:

• Clear 
• Red
• Green, yellow, or murky like dirty dishwater

Causes

When friction or injury occurs, your skin may respond by developing a blister. Blisters are a protective response that cushion the deeper layers of the skin, insulating it from damage and giving it time to heal.

In the case of an infection, your immune system causes blisters. When your body detects germs, your skin may break out as a response to fighting those germs.  

Diagnosis

Blisters are common and often heal on their own. However, if you notice signs of infection, you should contact your healthcare provider. Signs you should get your blister checked out include:

• It's draining pus.
• It's red or inflamed.
• It's painful and hot.
• You have a fever.
• You have multiple blisters and don’t know the cause.
• You have underlying health problems, like diabetes or circulation problems.
• It has a foul smell.

A healthcare provider can diagnose blisters through a physical exam and by taking your medical history. If the reason isn't apparent (such as an injury or friction), they'll want to determine if an illness may be causing the blisters. Your provider may also order blood tests and skin cultures (a method used to find organisms causing an infection).

Organisms from the culture that are suspected of causing the infection might then be tested against different antibiotic medicines to establish which one will work best.

Treatment

Often, blisters don't require special treatment. However, there are some things you can do at home to make yourself more comfortable, reduce the risk of infection, and speed the healing process, including:

• Wash the blister with soap and water.
• Apply antibacterial ointment.
• Cover the blister with a bandage.

Change the bandage and moisturize the area daily until the blister falls off naturally.

In certain circumstances, your healthcare provider might help you manage blisters, including:

• With an infection: If your blister is infected, your provider will likely prescribe antibiotics.
• If it needs draining: If your blister is large and painful, your provider may drain it with sterile instruments.
• During an illness: If an illness causes your blister, your provider will advise you on treating the underlying condition.

Prevention

While you can’t always predict an injury, there are some things you can do to limit your chances of getting a blister. These include:

• Wear properly fitting shoes.
• Always wear socks with your shoes.
• Wear protective gloves while working.
• Apply sunscreen.
• Wear weather-appropriate clothes.
• Slowly raise your body temperature with lukewarm water if you have frostbite.

Summary

Blisters are fluid-filled bubbles between layers of skin. They occur as a result of injury, friction, or illness. Blisters often heal on their own within a week. However, if your blister has signs of infection, is very large and painful, or you have an underlying health condition, you should seek medical advice. To limit the chances of getting a blister, wear shoes that fit well and gloves when you work, and use good hygiene to prevent illness.

A Word From Verywell

Blisters are usually a mild annoyance. If you have a blister, it's tempting to pop it, but don't. Popping a blister increases the likelihood that your sore will become infected. Instead, the best course of action is to keep the blister clean and cover it with a bandage until it heals.