CHAPTER 168
Friction Blister
Presentation
After wearing a pair of new or ill-fitting shoes or having gone on an unusually long hike or run, the patient complains of an uncomfortable open or intact blister on the posterior heel or ball of the foot. Occasionally, these blisters will be hemorrhagic. Secondary infection may be the cause of the visit, after painful pustules, cellulitis, or lymphangitis develops.
What To Do:
For torn or open blisters or blisters that have become infected, remove the overlying cornified epithelium with fine scissors and forceps. Clean the area thoroughly with a nontoxic skin cleanser (e.g., 1% povidone-iodine solution). Cover the wound with antibiotic ointment that does not contain neomycin and with a simple strip bandage. Have the patient wash the area and repeat the dressings until complete healing has taken place. It usually takes about 5 days for a new stratum corneum to form.
When cellulitis or lymphangitis is present, provide appropriate antibiotics (see Chapter 166).
For small (less than 1 cm) untorn or closed blisters that are not infected, the skin may be left intact and covered with a protective dressing.
To provide comfort for lesions larger than 1 cm, the blister can be decompressed. Cleanse the area with povidone-iodine; then, using a 25-gauge needle, aspirate the blister fluid until the blister has completely collapsed. To prevent contamination and infection, either provide continuous antibacterial ointment (bacitracin) and strip bandage protection, or cover the punctured blister with a polyurethane film (such as OpSite) or a hydrogel dressing (such as Spenco 2nd Skin or Vigilon), or seal the needle puncture with cyanoacrylate (Dermabond). Other acceptable protective coverings include the hydrocolloid, Duoderm; the occlusive dressing, moleskin; or the over-the-counter (OTC) liquid bandage, New-Skin. Additional padding may also be protective and comforting.
Instruct the patient about friction blister prevention. A properly fitting shoe is essential, and even comfortable shoes need to be broken in gradually. Walking and running activities should be slowly increased day by day. Good socks with moisture wicking and padded insoles can also help prevent friction blisters. Wearing two pairs of socks that are made of different materials may reduce skin friction and prevent blisters. United States Military Academy cadets who applied an antiperspirant solution containing 20% aluminum chloride to their feet for at least 3 consecutive days reduced their risk for developing foot blisters during a 21-km hike by approximately half. The use of such antiperspirants unfortunately causes a high incidence of skin irritation.
What Not To Do:
Do not use neomycin-containing ointments because of the potential for allergic reactions.
Do not unroof sterile blisters. This will lead to unnecessary discomfort from the denuded area as well as increase the risk for infection.
Discussion
Blisters result from frictional forces—compounded by perspiration—that mechanically separate epidermal cells at the level of the stratum spinosum. This usually occurs when there is inadequate time to develop the protective epidermal hyperplasia that normally occurs with gradual increases in friction stress. Hydrostatic pressure causes the resultant separation to fill with a fluid that is similar in composition to plasma but has a lower protein level.
Active people often develop friction blisters on their feet. Although such blisters rarely cause significant medical problems, they can be quite painful and hinder athletic performance. Treatment goals include maintaining comfort, promoting healing, and preventing infection.
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