Influence of an antiperspirant on foot blister incidence during cross-country hiking.

BACKGROUND: Rubbing moist skin results in higher frictional forces than rubbing very dry skin. As friction increases, the probability of activity-related blisters also increases. Therefore reducing moisture may reduce blister incidence during physical activity.

OBJECTIVE: We examined whether an antiperspirant can reduce foot blisters during hiking.

METHODS: In a double-blind study, cadets attending the US Military Academy were separated into two groups that used either an antiperspirant (20% aluminum chloride hexahydrate in anhydrous ethyl alcohol) or placebo (anhydrous ethyl alcohol) preparation. Cadets were told to apply preparations to their feet for 5 consecutive nights. On day 6, cadets completed a 21-km hike, and their feet were examined for blisters before and after.

RESULTS: Because of dropouts, the final sample size was 667 cadets with 328 in the antiperspirant group and 339 in the placebo group. There was a high rate of noncompliance with the treatment schedule: Cadets used the preparations from 0 to 5 nights before the hike. For cadets using the preparations at least 3 nights before the hike (n=269), the incidence of foot blisters was 21% for the antiperspirant group and 48% for the placebo group (P < 0.01). However, reports of skin irritation were 57% for the antiperspirant group and 6% for the placebo group (P < 0.01).

CONCLUSION: A 20% solution of aluminum chloride hexahydrate in anhydrous ethyl alcohol may be effective in reducing foot blisters during hiking; however, the side effect of skin irritation should be considered and preventive measures studied to reduce this irritation.