Background
Friction blisters of the skin commonly occur in active populations. They are the result of frictional forces between the involved skin area and the object with which the skin is in contact. Friction blisters create localized discomfort; however, they should not be taken lightly because secondary impetigo may become a serious complication with resulting cellulitis and sepsis.[1]
The bulk of research on friction blisters comes from the military because of the nature of the physical activity involved in this field. Friction blisters have also received much attention in the field of sports medicine.
See the image below.
View Image | Friction blisters on human foot. Courtesy of Andry French (own work), via Wikimedia Commons. |
Pathophysiology
The influence of epidermal hydration on the friction of human skin against textiles was studied. Increasing cutaneous hydration may cause sex-specific changes in the mechanical properties and/or surface topography of human skin, leading to skin softening and increased real contact area and adhesion.[2]
Studies involving rubbing the skin with a constant force show an initial slight exfoliation of the skin over the involved area. Focally, mild erythema also develops. The patient may experience stinging or burning, while a zone of pallor develops around the erythematous area. The pallor eventually extends into the region of erythema and this area develops into a blister.
The effect of wearing socks with different frictional properties on plantar shear was studied because this is a possible mechanical risk factor for foot lesion development.[3] Wearing socks with low friction against the foot skin reduced the plantar shear force on the skin more than a sock with low friction against the insole.
Friction blister formation is affected by epidermal hydration. In a study of 11 men and 11 women, the friction between the inner forearm and a hospital fabric was measured in different hydration states.[4] Increasing skin hydration caused sex-specific changes in the mechanical properties and/or surface topography, as the friction of female skin demonstrated significantly higher moisture sensitivity.
Technology such as thermographic images may facilitate assessment of traumatically damaged foot skin.[5]
Etiology
Poorly fitting shoes are the most common cause. Heat, sweating, and maceration of the skin may predispose to friction blister formation. A study of foot blister formation in 3 groups of 11 participants showed biomechanical interactions on the plantar surface of individuals prone to blisters to be at variance from less predisposed to this finding.[6] Baseball pitchers suffer repeated trauma between the baseball seams and the fingers of the pitching hand, most often at the tips of the index and long fingers.[7]
Epidemiology
Frequency
During the first Iraqi War, the prevalence of foot friction blisters among American troops was 33%, of which 11% required medical care.[8]
Race
No known predilection is reported for any particular race.
Sex
No known predilection is described for either sex. Women aged 26-34 years who are unable to break in their boots and have a past history of blisters, were the most likely to develop friction blisters among American troops during the first Iraqi War.[8]
Age
No known predilection is apparent for any age group.
Prognosis
Friction blisters create localized discomfort; however, they should not be taken lightly because secondary impetigo may become a serious complication with resulting cellulitis and sepsis.
Patient Education
Educate patients about the importance of prevention measures (see Prevention).
For patient education resources, see the Bacterial and Viral Infections Center and Skin, Hair, and Nails Center, as well as Impetigo, Skin Rashes in Children, and Antibiotics.
History
Friction blisters tend to occur in areas of thick adherent stratum corneum (eg, palms, soles, heels, dorsa of fingers). In regions of the body where the stratum corneum is thinner, a repeated friction force causes the stratum corneum to erode, and instead of a blister, an erosion or abrasion occurs. Children often present with poorly fitting shoes and reporting a blister on the heel.
The likelihood of forming a friction blister at susceptible sites is based on the magnitude of the frictional force and the number of times an object moves across the skin (ie, shear cycles). Moisture and lubricating substances present on the skin surface are additional factors. With a greater frictional force, fewer cycles of rubbing against the skin are needed to produce a blister. Hand blisters are an occupational hazard in major league baseball pitchers.[7]
Moisture on the skin surface may either increase the friction force or, in the case of very moist skin, decrease it temporarily by providing lubrication. Lubricating agents also tend to reduce the friction force temporarily at the onset; however, friction tends to increase with prolonged application of the external force.
Pyogenic granuloma on the hand has been described subsequent to a friction blister in a hand surgeon.[9]
Physical Examination
Discrete bullae formation at sites of trauma is evident, as seen in the image below.
View Image | Friction blisters on human foot. Courtesy of Andry French (own work), via Wikimedia Commons. |
Complications
Impetigo may become a serious complication, with resulting cellulitis and sepsis.
Histologic Findings
The friction blister forms with a split in the stratum spinosum. Midepidermal necrosis is evident. The blister roof consists of normal and necrotic keratinocytes; the blister floor consists of normal, edematous, and degenerating keratinocytes. The blister cavity is filled with a clear transudate. High mitotic activity is present in the base of the blister about 30 hours after formation of the friction blister. A significant inflammatory infiltrate is not observed as long as the blister site is not secondarily infected.
Medical Care
Management of friction blisters includes sterile drainage of the site while leaving the blister roof intact to serve as a dressing. This method helps relieve some discomfort and protects the site from superinfection. A donut of moleskin may also be applied to minimize additional trauma to the blister and to relieve discomfort. If the blister roof is already fully or partially removed, treat the site as an open wound with appropriate antiseptic and surgical bandage application. Hydrocolloid dressings have also been proven to decrease discomfort and encourage healing. Some recommend debridement of the skin of the blister, the use of a topical containing nitrofurazone, and the application of a bandage.[15]
Optimal therapy for blisters after prolonged walking is unclear.[16] A study compared two different regimens, wide area fixation dressing versus adhesive tape, evaluating 907 participants in Holland (aged 45 ±16 years, 52% men) who received 4131 blister treatments.[16] Owing to diminished effectiveness and satisfaction, use of wide area fixation dressing was not favored over adhesive tape for routine first-aid treatment for friction blisters.
Prompt attention to friction blisters is important to prevent the development of secondary impetigo with possible cellulitis and sepsis. Institute appropriate systemic antibiotic therapy if impetigo develops. Use of povidone-iodine solution (Betadine) may be beneficial.[17]
Prevention
Foot blisters, caused by frictional forces, can be prevented by wearing properly sized boots, conditioning feet through regular road marching, wearing socks that reduce friction and moisture, and possibly use of antiperspirants to the feet.[18] Increased cutaneous surface hydration enhances the rate of skin temperature change and the risk of blister formation.[19] Prevention of friction blisters has focused on antiperspirant agents and appropriate footgear.[20, 21] Antiperspirant agents decrease the likelihood of developing friction blisters, but their use is confounded by a high incidence of irritant contact dermatitis. Since increased skin surface hydration may be a risk factor for blister formation, a product that lowers skin hydration might be useful. Three different preventative foot blister commercial products were tested on 30 apparently healthy adults. Only the powder product was beneficial.[22]
The incidence of friction blisters on the feet may be somewhat decreased by the use of neoprene insoles, acrylic-based socks, or thin polyester socks combined with a thick wool or polypropylene sock that can maintain its bulk in the presence of moisture from sweat and compression.[23, 24, 25, 26, 27] Appropriately fitted shoes also are helpful in the prevention of friction blisters.
Friction blisters, which occur when shear loading causes the separation of dermal layers, were avoided when a triglyceride lubricant with T-shirt knit cotton was used.[28] The results of such textile and surface treatment performance are of value.
Sock fabrics may have distinct moisture properties when tested in a realistic military setting. One pair of socks 99.6% polypropylene and 0.4% elastane was compared with a blend of 50% Merino-wool, 33% polypropylene, and 17% polyamide, one on each foot. In this study, the blend stored almost 3 times more moisture, making it more desirable that the polypropylene socks.[29]
Paper tape was not found to be particularly protective against blisters in marathoners, although this intervention was well tolerated and had high user satisfaction.[30]
Medication Summary
Institute appropriate systemic antibiotic therapy if impetigo develops.
Author
Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Pathology, Professor of Pediatrics, Professor of Medicine, Rutgers New Jersey Medical School
Disclosure: Nothing to disclose.
Coauthor(s)
Kuljit Chima, MD, Assistant Attending Physician in Clinical Dermatology, Columbia University Medical Center
Disclosure: Nothing to disclose.
W Clark Lambert, MD, PhD, Clinical Professor of Pathology, Clinical Professor of Medicine (Professor of Dermatology), Rutgers New Jersey Medical School; Professor of Pathology, Rutgers Graduate School of Biomedical Sciences
Disclosure: Nothing to disclose.
Specialty Editors
Michael J Wells, MD, FAAD, Dermatologic/Mohs Surgeon, The Surgery Center at Plano Dermatology
Disclosure: Nothing to disclose.
Chief Editor
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Robin Travers, MD, Assistant Professor of Medicine (Dermatology), Dartmouth University School of Medicine; Staff Dermatologist, New England Baptist Hospital; Private Practice, SkinCare Physicians
Disclosure: Nothing to disclose.
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