Author: Hon Assoc Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2013.
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.
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.
Shear 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:
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.
Rubbing on the skin first peels off surface cells. More pressure causes the affected skin to redden, heat up and to sting. The red skin then becomes pale as the blister forms. The blister usually contains clear fluid but bleeding changes the colour to red/brown.
Blisters occur where the stratum corneum (the outer cell layer) is very thick, as is the case on the sole of the foot and palm of hands. Where the skin is thinner, friction tends to shear off the epidermis completely, resulting in an erosion (sore).
If the blister remains intact, the fluid will resorb and the damaged skin will peel off some days later.
Tests are not necessary for typical friction blisters. The following investigations may be considered when blistering is frequent, extensive or failing to heal.
Intact friction blisters usually heal up quickly without scarring. Healing is sometimes delayed. Problems may include:
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.
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).
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