October 2, 2012 .How to Prevent and Treat Blisters
By Dr. Cathy Fieseler
Blisters are a common skin injury in active people, especially runners; although they are not life threatening, blisters can significantly affect one's ability to continue an activity.
The skin is comprised of three layers: the epidermis, the dermis and the subcutaneous tissue. The epidermis is the outermost tissue and is comprised of five layers. The dermis contains specialized structures, such as hair follicles and sweat glands. The subcutaneous tissue is comprised of fat and connective tissue and plays an important role in temperature regulation.
Blisters are the result of repeated friction on the skin surface. This creates a shear force which separates the skin into two layers; this space then fills with fluid as the result of hemodynamic forces.
The location of the space that is created is dependent on the thickness of the tissues. Sites where the epidermis is thin (sides of toes), the separation occurs between the epidermis and the dermis; sites where the epidermis is thick (plantar aspect of the foot), blisters form within the epidermis.
The stratum corneum (outermost layer of skin) must be sufficiently thick to withstand the friction on the surface; otherwise an abrasion (chafing), not a blister forms (as would occur on the inner thigh). Blisters are an acute response to higher intensity stresses, whereas chronic low intensity stress causes callus formation.
A number of factors contribute to blister formation; these factors contribute to frictional forces. Intrinsic factors (anatomic variations) include: toe deformities (i.e. bunions, hammer toes) and abnormal foot biomechanics and malalignments. External factors include: activity level, shoes and socks, and terrain. Each of these factors may cause increased pressure and friction on various parts of the foot.
In addition to friction, moisture and heat are significant factors in the formation of blisters. Moisture is an especially critical factor in blister formation; friction forces are lower when feet are either very dry or very wet as compared to moist feet.
In order to prevent blisters, one or more of the predisposing factors (moisture, friction, and heat) must be minimized or eliminated.
1. Adaptation -- The skin will adapt to repeated friction. There is increased cellular regeneration; the younger cells are more resistant to blister formation.
2. Shoe fit -- Shoes should be tried on late in the day, to allow for swelling of the feet. Athletic socks and orthotics should be worn when trying on shoes. The location of blisters can indicate specific shoe problems. Blisters on the heel suggest that the heel cup is too wide. Blisters on the dorsal surface or tips of the toes, or on the outer borders of the first and fifth toes suggest a problem with the toe box.
3. Socks -- Socks can decrease moisture or friction. Synthetic socks have wicking properties which decrease moisture. Double layer socks decrease shear forces but also decrease wicking abilities. Wool socks work very well for some runners. Choice of socks should be personal preference. Socks should fit snugly.
4. Antiperspirants -- Antiperspirants decrease moisture. There is a significant incidence of irritant dermatitis with the use of antiperspirants. Moisturizing creams decrease the incidence of dermatitis but also decrease the effectiveness of antiperspirants.
5. Drying powders -- Powders are advocated for moisture absorption. Studies have shown that wet powder clumps and actually increases friction forces.
6. Lubricants -- Skin lubricants decrease friction. This is effective for only a short period of time. After one hour, shear forces return to baseline. After about three hours, friction forces are greater than baseline levels.
7. Skin tougheners -- These substances form a protective coating and toughen the skin. Application of tincture of benzoin, and soaking in tea or betadine can be used for this purpose. These methods also improve the adherence of tape. Beware: these substances will discolor the skin (and most surfaces they come in contact with).
8. Orthotics -- Correcting functional abnormalities will decrease abnormal forces on the foot. Use of orthotics in running shoes will affect the fit of the shoe and possibly create pressure points.
9. Shoe laces -- Laces can create pressure points. Using different lacing techniques can eliminate pressure points and correct problems like heel slippage.
10. Gaiters -- These devices go over the shoe and ankle, and prevent dirt and rocks from getting into the shoe. These irritants increase friction. Gaiters are useful for athletes involved in off-road activities.
11. Insoles -- There is evidence that insoles decrease the incidence of blisters. This is felt to be due to decreased shear forces. Don't forget that adding an insole will affect the fit of the shoe.
12. Changing shoes and socks -- Changing socks frequently keeps them dry and clean. If lubricants are used, this allows for frequent reapplication. Frequent shoe changes will minimize accumulation of debris. Different shoes have different pressure points, which may also help decrease the incidence of blisters. Although this is not practical during a marathon, ultrarunners often change shoes during a race.
13. Foot nutrition -- The daily application of creams or lotions will keep the calluses soft and reduce pressure points.
14. Hydration -- Dehydration causes loss of skin turgor; skin folds predispose to blistering.
15. Sodium -- Hyponatremia may occur during prolonged events; this causes swelling of the hands and feet. The soft, swollen tissues are especially vulnerable to shear forces.
16. Taping -- Tape forms a barrier between the skin and socks, reducing friction forces. Many different types of tape are available. Elastic, porous tape conforms to the foot and is very effective in preventing blisters. Ultrarunners may use duct tape to prevent blisters.
Fixing Your Feet by John Vonhof is an excellent resource on foot care in athletes.
How to Treat Blisters
(Ed Note -- Wash the blister. Pop it with a sterilized needle and drain it. Cover the blister with Spenco Second Skin (or similar product), taping the Second Skin with paper adhesive tape or light cloth tape. I find that the tape that is included with Second Skin gives me blisters (ironic). You'll now be able to run pain-free while you address the cause of the blister. If you are blister prone, consider purchasing Second Skin disks at a healthcare products retailer).
Dr. Fieseler is the Director of Sports Medicine for the Trinity Mother Frances Health System in Tyler, TX. She is a regular contributor to Running Times and has served as the chairperson for the sports medicine committee of the Road Runners Club of America.
© 2012 Savvy Runner Inc.
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