What is a friction blister?

A friction blister is a blister caused by the skin repeatedly rubbing against another object. It most often forms on the palms, fingers, soles, sides of the feet and toes. The top of the blister is rubbed off where skin is thinner, such as the top of the hand or foot, forming an abrasion. In areas of thinner skin, friction causes chafing without blistering.

Friction blisters will heal on their own. However, dressings are helpful to protect from further damage. Hydrocolloid blister plasters may promote faster healing.

Large blisters can be drained by pricking with a sterile needle. It’s best to keep the roof of the blister in place if possible, to reduce pain and lessen the chance of infection. If the roof of the blister has come off leaving an eroded skin surface, clean the wound carefully and apply a clean dressing.

Infected friction blisters or erosions may require topical antibiotics or antiseptics for a few days. Systemic antibiotics must be used if cellulitis occurs. Antibiotics should not be used if the wound is not infected.

If prone to friction blisters, the following measures may be useful.

• Well-fitting boots and shoes; use orthotics if necessary to reduce pressure points.
• Neoprene insoles
• Moisture absorbent socks, changed as soon as they are damp
• 2 pairs of socks: thinner inner polyester layer and thicker wool or polypropylene outer layer
• Gaiters to prevent gravel and plant materials entering the footwear
• Lamb’s wool padding over and around areas prone to blister
• Various proprietary foam padding, cushioning and protective barrier products, which are available at the shoe counter of your local pharmacy

Antiperspirant, petroleum jelly or silicone lubrication, powders and topical skin adhesives have been advocated and may prove useful. However, they have not been shown scientifically to reduce discomfort or improve healing.

Some hardening occurs with repetitive low intensity exercise because of callus formation (epidermal thickening).

What causes friction blister?

A friction blister occurs when there is contact, pressure and movement between the skin and something touching it – such as a heel rubbed by a new or unfamilar shoe.

Sheer forces cause mechanical separation of the layers of epidermal cells. The gap fills with fluid, forming a subepidermal bulla (blister). A blister forms more quickly if pressure and movement on the skin is severe or the skin is damp.

Friction blisters occur from time to time in nearly males and females of all ages. Exacerbating factors include:

• Heat — they are particularly prevalent in tropical climates.
• Prolonged or vigorous exercise — they are common in athletes (especially marathon runners) and soldiers; one third of 872 American soldiers surveyed when in Iraq had friction blisters ¹. Blisters on the palms may arise from rowing, or in children playing on monkey bars.
• Carrying a heavy load increases the risk of blisters.
• Excessive sweating — hyperhidrosis softens the skin so the skin splits more easily.
• Tight, uncomfortable or new shoes, which repetitively rub on one or two areas of skin.
• Unabsorbent or thin socks — these do not absorb moisture well and do not protect the skin adequately from damage by shoes or boots.
• Rough or hard fabrics may cause blisters on other sites, such as armpits or groin.

Blisters may also arise on pressure areas such as the hip, as a complication of surgery or loss of consciousness, classically following barbiturate poisoning.

There are some specific diseases that make the skin more fragile than usual, also causing blisters in response to friction or injury.

• Genetic disposition — epidermolysis bullosa is a group of disorders in which the skin blisters easily.
• Immunobullous disease — epidermolysis bullosa acquisita.
• Metabolic disease — porphyria cutanea tarda
• Sun damage — especially overexposure to solaria or tanning beds
• Certain medications — pseudoporphyria due to nonsteroidal anti-inflammatories or antibiotics (doxycycline).

Friction blister prevention

While you often think of friction blisters on your feet, these painful skin irritations can occur anywhere on your body where body parts rub together or rub against clothing. Fortunately, friction blisters can be prevented by preventing chafing. To stop them before they appear, pay attention to your skin and take precautions if you know you’re going to do a lot of walking, running or other physical activity.

1. To prevent friction blisters on your feet, wear shoes that fit well. It also helps to use moisture-wicking socks. Try the various socks, shoes and insoles that are designed specifically to help reduce blistering. You might also try attaching moleskin to the inside of your shoe where it might rub or dusting the inside of your socks with talcum powder. Gloves help prevent blisters on your hands.
2. Wear the right clothing: During physical activity, wear moisture-wicking, loose-fitting clothes. Avoid clothes made of cotton, as cotton soaks up sweat and moisture, which can lead to friction and chafing.
3. Consider soft bandages: For problem areas, such as the feet or thighs, consider using adhesive moleskin or other soft bandages. Make sure the bandages are applied securely.
4. Apply powder or petroleum jelly to problem areas: This helps reduce friction when your skin rubs together or rubs against clothing.
5. Stop your activity immediately if you experience pain or discomfort, or if your skin turns red: Otherwise, you may get a blister.

If you do get a blister, be patient and try to leave it alone. Most blisters heal on their own in one to two weeks. Don’t resume the activity that caused your blister until it’s healed.

To treat a blister, dermatologists recommend the following:

• Cover the blister: Loosely cover the blister with a bandage. Bring in the sides of the bandage so that the middle of the bandage is a little raised.
• Use padding: To protect blisters in pressure areas, such as the bottom of your feet, use padding. Cut the padding into a donut shape with a hole in the middle and place it around the blister. Then, cover the blister and padding with a bandage.
• Avoid popping or draining a blister, as this could lead to infection. However, if your blister is large and very painful, it may be necessary to drain the blister to reduce discomfort. To do this, sterilize a small needle using rubbing alcohol. Then, use the needle to carefully pierce one edge of the blister, which will allow some of the fluid to drain.
• Keep the area clean and covered: Once your blister has drained, wash the area with soap and water and apply petroleum jelly. Do not remove the “roof” of the blister, as this will protect the raw skin underneath as it heals.

As your blister heals, watch for signs of an infection. If you notice any redness, pus, or increased pain or swelling, make an appointment to see your doctor or a board-certified dermatologist.

Friction blister complications

Intact friction blisters usually heal up quickly without scarring. Healing is sometimes delayed. Problems may include:

• Pain impeding performance
• Wound infection: this presents with increasing pain and redness around the blister/erosion, a red streak heading for the groin or armpit, and pus formation. Infection is more common in diabetics and immune impaired individuals.
• Pyogenic granuloma may occasionally arise at the site of a blister some days later.
• Scarring due to infection or deeper injury.

Friction blister diagnosis

Tests are not necessary for typical friction blisters. The following investigations may be considered when blistering is frequent, extensive or failing to heal.

• Swab to check for bacterial infection with Staphylococcus aureus or Streptococcus pyogenes (impetigo or cellulitis).
• Skin biopsy of a new friction blister for histopathology reveals intraepidermal split without inflammation. Specific features may lead to another diagnosis.
• Skin biopsy for direct immunofluorescence, positive in immunobullous diseases, is negative in friction blister.
• Genetic tests may be requested if epidermolysis bullosa is suspected.

Friction blister treatment

Friction blister first aid

If a friction blister isn’t too painful, try to keep it intact. Unbroken skin over a blister may provide a natural barrier to bacteria and decreases the risk of infection. Cover it with an adhesive bandage or moleskin. Cut a piece of moleskin into a doughnut shape and place the pad so that it encircles and protects the blister. Then cover the blister and moleskin with gauze.

Seek medical care if the blister looks infected. If you have diabetes or poor circulation, call your doctor before treating the blister yourself.

How to drain a friction blister

To relieve friction blister-related pain, drain the fluid while leaving the overlying skin intact. Here’s how:

1. Wash your hands and the blister with soap and warm water.
2. Swab the blister with iodine.
3. Sterilize a clean, sharp needle by wiping it with rubbing alcohol.
4. Use the needle to puncture the blister. Aim for several spots near the blister’s edge. Let the fluid drain, but leave the overlying skin in place.
5. Apply an ointment such as petroleum jelly to the blister and cover it with a nonstick gauze bandage. If a rash appears, stop using the ointment.
6. Follow-up care. Check the area every day for infection. After several days, cut away all the dead skin, using a tweezers and scissors sterilized with rubbing alcohol. Apply more ointment and a bandage.

References

1. Brennan FH Jr, Jackson CR, Olsen C, Wilson C. Blisters on the battlefield: the prevalence of and factors associated with foot friction blisters during Operation Iraqi Freedom I. Mil Med. 2012 Feb;177(2):157-62.