INFLUENCE OF AN ANTIPERSPIRANT ON FOOT BLISTER INCIDENCE DURING CROSS-COUNTRY HIKING

Background: Rubbing moist skin results in higher frictional forces tha n rubbing very dry skin. As friction increases, the probability of act ivity-related blisters also increases. Therefore reducing moisture may reduce blister incidence during physical activity. Objective: We exam ined whether an antiperspirant can reduce foot blisters during hiking. Methods: In a double-blind study, cadets attending the US Military Ac ademy were separated into two groups that used either an antiperspiran t (20% aluminum chloride hexahydrate in anhydrous ethyl alcohol) or pl acebo (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 bef ore and after. Results: Because of dropouts, the final sample size was 667 cadets with 328 in the antiperspirant group and 339 in the placeb o group. There was a high rate of noncompliance with the treatment sch edule: 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 antiperspira nt 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 chlor ide hexahydrate in anhydrous ethyl alcohol may be effective in reducin g foot blisters during hiking; however, the side effect of skin irrita tion should be considered and preventive measures studied to reduce th is irritation.