Blisters : Causes And Management

Most hillwalkers and climbers will have suffered from blisters on their feet at some time. Their effects range from mildly irritating to debilitating depending on their severity, or how far from being able to get your boots off you are! If ignored or inappropriately treated they can become infected and pose a serious health problem. Although in size blisters appear insignificant, when burst and causing pain they can severely restrict mobility, affecting the walkers concentration and judgement.

What are blisters and how are they formed ?

Blisters are wounds caused by a combination of pressure and friction which when applied to the skin of the foot can lead to a gap forming between the layers of the skin. Into the gap that is created flows lymph fluid, as the layers of the skin remain intact at the edges of the blister the lymph cannot escape and so the detached layer of skin is raised up. After the layers of skin have become separated in can take up to two hours before the blister is filled. Once a blister has filled it is only a matter of time before it bursts if no action is taken to reduce the pressure and friction forces it is subjected to.

Pressure Friction and Moisture.

Large amounts of pressure and friction are required to develop a blister. Where small amounts of these factors are applied to the skin, it tends to respond by the formation of calluses. These calluses can be seen on the soles of the feet and on the hands. In situations where there is an increase in the normal amounts of pressure and friction, blisters can form in a very short time. Where footwear is to tight restrictive pressure can be applied to the prominent areas of the foot particularly the heel and the ball of the foot. Where socks have been allowed to loosen and form wrinkles pressure can build up as the sock occupies the small space between the foot and boot.

Friction describes the rubbing motion caused by each step. As the ball of the foot strikes the ground pressure is maximised upon the heel area and the heel striking the ground causes a small amount of movement between the foot, sock and boot. Vulnerable areas of the foot are subjected to a heavy rubbing motion. As a walk progresses so the forces are repeated and the skin becomes hot and the damage begins.

Damage caused by pressure and friction is exacerbated when the skin surface is moist, usually sweat or water leaking into the boot. Moisture softens the skin making it more susceptible to damage from pressure and friction.

Early warning signs of blister formation

Blister Prevention

Boots
Care should be taken to break in new boots around the house or on low level short walks before venturing further afield. After wearing the boots for a number of hours in the house a visual inspection should be undertaken of the feet. It should be remembered that any small slightly painful areas experienced while ascending the stairs of your house could become painful debilitating blisters after 10 miles on tougher terrain. Where the boots are giving problems due to hard edges etc they should be returned to the shop for advice or visit the local shoe maker for softening.
Socks
The choice of socks is vital as they can both reduce the pressure and friction applied to the skin while also reducing the amount of moisture on the skin surface. Thick socks that provide padding for the heel and sole of the foot will help reduce the chance of blistering. Socks made of an absorbent material such as wool will absorb some of the moisture on the skin, thus reducing the chance of softening the skin.
Skin Care
If you have suffered for blisters in the past it is very important to recognise that the tissue will be more susceptible to damage again. Vigilance will be required and it may be prudent to change in to fresh socks on hot days when extra moisture will be present on the skin surface. Some people advocate the use of Vaseline on the skin to reduce friction, while this idea could be useful on a long walk frequent stops would be required to re apply the gel. Keeping the skin dry is important and to this end talc may be useful.

Treatment

What if your best laid plans fail and you develop a blister. Many different treatments /tortures have been used in the past, the author has focused on the more rational options! There are two distinct schools of thought regarding the treatment of an intact blister, with little research to support one over the other. Both are discussed below, each to their own.

Treatment of an intact blister

Option one
It is suggested that where a blister is intact treatment should focus on preserving the status quo and if left alone the blister will heal on its own without infection. This is done by reducing the pressure on the blistered area by the use of for example a corn plaster placed around the damaged tissue. Theoretically this should prevent the application of pressure or friction to the affected area. This can be covered over with a large fabric plaster or sports tape. Care should be taken to ensure that the adhesive of the tape does not come into contact with the damaged skin as this might lead to bursting when removed. This method can take some time to master but the author has had some success particularly with small blisters.
Option two
Others believe that as the blister was formed as a result of pressure and friction, once back in the boot the foot will be subjected to the same forces as caused the injury. Therefore it will be very difficult to prevent the blister bursting of its own volition. Where a blister has been found intact it should be swabbed with an antiseptic, drained using a sterile needle and the liquid gently squeezed out. Any loose skin should be removed from over the wound, careful hygiene should be observed to reduce the chance of infection. A dressing designed to provide a moist healing environment and able to withstand the pressure and friction placed upon on the wound while walking.

Treatment of a burst blister

In the event of a blister bursting the loose skin should be removed. Where possible the foot should be washed in water and cleaned with an antiseptic swab. Since the 1960s it has been recognised that wounds heal faster if they are occluded and kept in a moist environment, this also reduces the chance of infection. Traditional plasters should not be used as they fail to occlude the wound nor do they provide a moist healing environment. Instead a modern wound management product should be chosen. Most of the treatments available in pharmacies are Hydrocolloids, adhesive dressings with a film backing. Hydrocolloids are interactive dressings with a brown base which becomes a yellow gel after contact with wound exudate. The gel provides a moist environment thus promoting wound healing. While allowing gas to escape from the wound the dressing does not allow contamination from the environment in to the wound, reducing the risk of wound infection. Any product chosen should adhere to the following criteria.

Conclusion

Foot blisters have afflicted hillwalkers and climbers for generations but they are for the most part preventable. Where they have occurred their management should not pose any major problems to the prepared walker. When left to their own devices they will detract from the day or could lead to infection. Large blisters could slow the pace of a walker which in difficult conditions could have serious consequences.

The Department of Tissue Viability is currently conducting research into blisters experienced by hillwalkers. Clinics are held (in Aberdeen) on Mondays 2pm-8pm to arrange an appointment contact 01224 552328.

David Gray, October 2000

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