If you're going to believe something, make sure that there is some science behind it. So when I tell you that deodorant can prevent blisters, don't believe me, believe the science.
The background: a test was done at the US Naval Academy where two groups were put to the test. One group used antiperspirant mix and the other group a placebo on their feet before a long hike. Tin summary, 50% fewer blisters were found on the feet that used the antiperspirant solution. The complete results can be found below.
As for my personal experience, when I hike with new shoes I either wear double socks or I treat my feet to a quick rub of underarm Arm & Hammer UltraMax Antiperspirant and Deodorant until the shoes are broken in and ready for longer hikes.
Why do I do this? I have found is that the underarm deodorant does two things; first, it acts as a lubricant under the toes and one the heel, and second, the antiperspirant wicks away moisture from my feet.
I rarely get blisters using this method.
If you are doing long distance hikes, like the Camino de Santiago, where you are doing 20 miles a day for 30 days, you do not want blisters or it will be a good walk spoiled.
Not all shoes give me blister, but some do, with those I run my feet down with the Arm & Hammer UltraMax Antiperspirant and Deordorant.
Just for the record, this is not the same container that I use under my arms, I have a unique container for my feet. My feet smelling fresh is just a side bonus. :-)
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.
We examined whether an antiperspirant can reduce foot blisters during hiking.
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.
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.
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.