What are blisters?

Blisters are fluid-filled skin lesions. They are caused by burns, contact dermatitis, friction and certain medical conditions.
Blisters are fluid-filled skin lesions. They are caused by burns, contact dermatitis, friction and certain medical conditions.

Blisters are lesions on your skin that are filled with fluid. They are caused by friction, burning, disease, or other damage to your skin. Foot blisters are a common occurrence, and there are many reasons why they develop. Fortunately, most can be easily treated. 

Signs and symptoms of foot blisters

Most blisters develop on the outermost layer of a person’s skin. They are typically red and stick out from the skin, and they are usually painful when touched. If the area where the blister has developed continues to be irritated, the pain can get worse and the skin may tear.

Causes of foot blisters

Burning

A blister will develop on the skin when it has been burned. The blister is the body’s response to protect underlying tissue layers from being further damaged. The size and severity of the blister will depend on what caused the burn

Sunburn and other types of first-degree burns may cause a blister to form after a day or two. More severe, direct burns will typically produce a blister immediately.

Contact dermatitis

Contact dermatitis occurs when the skin is exposed to a foreign substance that irritates it or produces an allergic reaction on the skin. Human-made chemicals like gasoline, or plants found in nature like poison ivy, are examples of foreign substances that can cause blisters to form. 

A blister will form if there is prolonged exposure to the irritating substance. Examples of things that can cause contact dermatitis blisters include: 

  • Chemicals found in solvents or cleaners
  • Chemicals found in washing detergents
  • Chemicals used in laboratory or clinical settings
  • Chemicals used in making skin cleansers
  • Chemical gases used in warfare
  • Insect bites and stings
  • Skin allergens (substances that cause allergic reactions on your skin)
  • Sulfates

Friction and pressure 

The most common causes of blisters on the feet are friction and pressure when the skin of the feet continuously rubs against a sock, shoe, or another rough surface. This will cause irritation and inflammation on the skin, resulting in a blister. The blister will cause pain, swelling, and redness in the area.

Medical conditions

Blisters can be caused by certain infectious diseases and disorders. Any ailment that weakens the outer layer of the skin can make it more vulnerable to blisters.

Medical conditions and treatments that can cause foot blisters include:

Diagnosis for foot blisters

Blisters normally heal within a week after they surface. You should see a doctor, however, if a blister becomes discolored or inflamed, or your pain worsens. Blisters that turn green, yellow, or purple may suggest that the wound has become infected and requires medical attention.

Doctors can diagnose a blister by visually examining the affected area. They may drain a blister if it becomes noticeably infected, is extremely disabling or painful, or doesn’t go away. They will use a sterilized scalpel or needle and usually take a small sample of the blister for laboratory testing.

Treatments for foot blisters

Blisters will usually heal on their own after a couple of days. While picking or bursting a blister might be tempting, you should leave it intact because an open blister can become infected.

Cover a blister with a bandage to protect it while it heals.

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Medically Reviewed on 1/8/2021
References
SOURCES

Institute for Preventive Foot Health: "Causes of Blisters."

Institute for Preventive Foot Health: "Prevention and Treatment of Blisters."

National Health Service: "Blisters."