Lots, including washing a lot and keeping these areas as dry and cool as possible.
As you may have noticed, sweat, which helps regulate body temperature, smells different in different parts of the body. That’s because the skin contains different kinds of glands. The more common are the eccrine glands, which pump out salty water (sweat).
Sweaty feet smell bad because of bacteria that feed off this sweat and dead skin, said Dr. Robert Stern, chief of dermatology at Beth Israel Deaconess Medical Center. Some strong odors, like garlic, are also pumped out in sweat, he said. The bad smell of athlete’s feet is due to a combination of fungus and bacteria.
The armpits and groin also contain apocrine glands, which pump out a number of substances, including mate-attracting pheromones.
To combat odor, you can, in addition to washing, use baby powder to sop up sweat, leaving less for bacteria to feed on. Anti-perspirants reduce sweat by blocking eccrine glands. Deodorants are really just perfumes, though some also contain anti-perspirants.
For really bad foot odor, some people swear by anti-microbial socks that contain silver-coated nylon, which may inhibit the growth of bacteria. Other people swear by insoles containing super-activated charcoal and baking soda.
For people who sweat profusely, a condition called hyperhydrosis, a liquid solution called Drysol (available by prescription) can help “shrivel up sweat glands,” said Dr. Samuel Ahn, chief of endovascular surgery at the UCLA David Geffen School of Medicine. Botox injections, which deadens the nerves that trigger sweating, also helps, especially in the armpits. (Feet are too big and too sensitive for the 60 to 100 injections it would require.)
As a last resort, there’s surgery to remove pieces of the sympathetic nerves that supply the hands, armpits or feet. It can help, but a major risk is that it may actually increase sweating on the trunk.