by Di Challen

A friction blister is an accumulation of blood or fluid between skin layers. A blister starts to form when a sock clings to damp skin. The friction from walking then causes the skin to be dragged back and forth across the underlying tissue, and the resulting tear in the upper layers of the skin fills with fluid. Reducing friction and moisture can decrease blister formation.

To avoid blisters, try some of the suggestions below:

• Purchase shoes that have been properly fitted. Allow room for the swelling that will occur when feet are hot, and consider the type of sock you will wear with the shoe - thick socks can reduce the volume of a shoe.
• Wear-in new shoes before competing in them. Shoes and boots constructed from inflexible leather will take more wearing-in than a conventional running shoe.
• When training wear the same shoe you intend competing in - if not all the time, at least on a regular basis.
• Condition the feet to prolonged walking or running.
• Wear wool or wool/synthetic “tube” socks that do not bunch up or crease. A synthetic (eg polypropylene) inner liner may further reduce blistering by wicking moisture away from the skin. It should be worn inside a wool or wool blend sock. Wearing two pairs of socks my have a second advantage; apparently the outer sock (which is moved by the boot) will rub against the inner sock rather than the skin, thus reducing friction. Avoid socks made from cotton or cotton blends.
• Wear gaiters that cover the entire opening at the top of the shoe. Even minute foreign objects that enter the shoe, such as grains of sand, can cause blisters.
• Tape vulnerable areas with a smooth-surfaced adhesive tape that will not become peel away if the foot becomes wet. Scholl moleskin, Leukosilk, Leukoplast and Elastoplast elastic adhesive plaster are good products, although personal experience has shown that blisters will occasionally form at the edges of Elastoplast.
• Coat feet with a generous amount of petroleum jelly or lanolin to minimise friction.
• Powder feet to reduce moisture.
• During the event treat “hot spots” immediately by taping. Although you will lose time, it may prevent the formation of a painful blister that could slow you down later on.
• Remove shoes and socks if a water crossing means getting your feet wet. Waterproofing shoes against rain and dew may also prevent wet feet to some extent.
• Do not remove shoes and socks if a water crossing means wet feet! Some rogainers insist that their feet are less likely to blister when wet.

To treat blisters, try some of the following measures:

• Place a piece of gauze or foam over the blister and tape into place. Other products for covering blisters include Compeed Skin Protector, 3M Flexible Foam Sports Tape and Handyplast Blister Dressing. Tape by itself may be adequate, although when removed, it will probably tear away the roof of the blister.
• If the blister continues to cause discomfort, it may need to be lanced and drained. The incision should be large enough to ensure that the blister cannot seal itself and fill up with fluid again. Do not remove the layer of skin covering the blister as this will protect the underlying skin from further abrasion. (Ideally precautions should be taken to avoid infection, including cleaning the area first, using a sterile lancing instrument and dressing the area with antibiotic ointment afterwards. This is usually not practical during a rogaine!) Tape or cover the area with one of the products listed in the above paragraph.
• A very effective (although relatively expensive) treatment is Spenco 2nd Skin, a breathable gel that reduces friction between moving surfaces, absorbs blood and fluid, and cools the area. A knit bandage or tape is required to hold it in place. Again, the blister must first be lanced and drained.
• Another useful product,which unfortunately is not readily available in Australia, is the Unna boot, a zinc oxide impregnated bandage that is held in place with an elastic bandage. The Unna boot is particularly good for blisters on the sole of the foot. The blister should first be incised and collapsed.

The best methods for preventing and treating blisters will differ from individual to individual. Finding the ones which are most effective may be a matter of trial and error; and the source of much pain and frustration!

REFERENCES
Bloomfield, J., Fricker, P.A. & Fitch, K.D. (1992). Textbook of Science and Medicine in Sport. Melbourne: Blackwell Scientific Publications.
Forgey, W. (1994). Wilderness Medicine: Beyond First Aid (4th ed.). ICS Books: Merrillville, Indiana.

I gratefully acknowledge the assistance of the pharmacists, pharmaceutical distributors, outdoor equipment retailers, fellow rogainers and friends who provided me with information and advice for this article.