A reader asks: For the past few years, I’ve developed blisters (and eventually thick calluses) on my big toe and the toe next to it, where the two toes touch. This happens on both feet once the weather warms up. I’ve tried roomier shoes, but that doesn’t seem to help. Is there anything I can do to prevent the blisters?
Blisters certainly can take the fun out of a run. And worse, they can be an entry for infection. The root cause is increased friction, but the question is what’s causing the friction? While it can be a variety of things, the four main culprits are shoes, socks, sweat, and restricted foot motion.
You seem to have controlled for the role of shoes in the equation by making sure you have adequate toe room. This is good: shoes that squeeze the toes or forefoot can increase friction between the toes and result in blisters.
Another possibility is trying a shoe with a shorter heel (also known as a heel-to-toe drop). A thicker heel could be forcing your toes into the toe box while you are running.
Another possibility is swapping out your insoles. The military is very interested in foot blisters and have looked at the influence of insoles with respect to blister formation. Their studies show that low friction insoles produce fewer blisters in military personnel, especially during the early physical training that is required.
Socks are also very important for foot skin health. Again, studies from the military show that double layer socks reduce blister formation. Or, invest in technical/compression socks designed for running and sports.
I used a combination of low-friction insoles and synthetic socks on the Inca Trail last year. I was coming off the winter months, when I had little time for hiking to condition my feet, yet I had no blister problems during my days on the trail, and the environment ranged from rainy and cool to hot, arid and sweaty. So I can attest that both strategies help reduce skin friction.
Then there is sweat. Since you seem to have more trouble in warmer conditions, try using commercially available antiperspirants with aluminium chlorohydrate. This is an old army trick passed on to me from my father who spent his working life in the military and was cold-weather trained.
When I complained of sweaty cold feet in the winter, he suggested I try an antiperspirant on my feet, which worked to keep my feet drier from the inside. It turns out the military has also studied this for blisters related to physical conditioning, which includes running and hiking, and found it effective for many troops.
If you try this, start with the lowest concentration of aluminium chlorohydrate to reduce any possible skin irritation that often accompanies the more concentrated formulations.
If none of these help, your blisters may be part of a problem with foot motion. There are a lot of joints in the foot and if one joint does not have a normal motion, it can disrupt the kinetic chain resulting in skin pressure and blistering.
Consult a healthcare provider who can do manual therapy to get the joints moving properly. You may need to search a bit for a provider who can both assess your foot motion and restore joint motion in your foot.