What are Friction Blisters?

Friction blisters are fluid-filled bumps that look like bubbles on the skin. Blisters often develop on high-friction parts of the foot that rub against the inside of shoes or boots. Blisters form as the result of heat from shearing forces within the skin that cause cellular distortion and eventual cell death of the middle layers of skin.

The extent of skin shear resulting in blister formation is influenced by a number of factors such as fitment of footwear, fabric of socks and liners, moisture levels, and breathability of footwear.

Signs & Symptoms

Friction blisters begin as tenderness or sensitivity at high-friction points of skin such as the heel and sides of the foot. As friction continues, the skin becomes inflamed and eventually develops a pustule (blister).

First-Aid for Blisters

• A small, unbroken blister about the size of a pea, even a blood blister, will usually heal on its own. Use a loose bandage to protect it. Avoid the activity that caused the blister.
• If a small blister is on a weight-bearing area like the bottom of the foot, protect it with a doughnut-shaped moleskin pad. Leave the area over the blister open.
• If a blister is large and painful or inhibits movement, it may be best to drain it. A safe method is to:
  • Wipe a needle or straight pin with rubbing alcohol or heat it with a flame.
  • Gently puncture the edge of the blister.
  • Press the fluid in the blister toward the hole so it can drain out.
  • If a person has a condition such as diabetes, HIV, cancer, or heart disease, you do not want to drain a blister because of the risk for infection.
• After draining a blister, or if it has torn open:
  • Gently wash the area with clean water. Do not use alcohol, iodine, or any other cleanser.
  • Don't remove the flap of skin over a blister unless it's very dirty or torn or there is pus under it. Gently smooth the flap over the tender skin.
  • Apply a thin layer of petroleum jelly, such as Vaseline^®, and a non-stick bandage.
  • Change the bandage once a day or anytime it gets wet or dirty. Remove it at night to let the area dry.

Watch for a skin infection while the blister is healing. Signs of infection include:

• Increased pain, swelling, redness, or warmth around the blister.
• Red streaks extending away from the blister.
• Pus draining from the blister.
• Fever.

Preventing Friction Blisters

Don't wear cotton socks during physical activity. Wear moisture-wicking socks made of synthetic material or wool to allow sweat and moisture to dissipate.

Proper-fitting footwear that has been broken in and taping / patching high-friction areas of the foot have been shown to decrease incidence of foot blisters¹.

Adapted from:
Blisters. HealthLink BC.
¹ M. D. Hoffman. Etiological Foundation for Practical Strategies to Prevent Exercise-Related Foot Blisters. [Review]. 2016. Current Sports Medicine Reports. 15(5):330-5.