When it comes to body odor, staying (or getting) clean is the biggest weapon in your arsenal. Here's a brief lesson in the science of sweat: The eccrine glands, which are located on almost every part of the body, produce body cooling sweat that's mostly water. Think of it as nature's little air conditioning system. The apocrine glands, which are located in the armpits and in the groin (among other areas), produce sweat that performs a number of functions, one of which is to work as a kind of waste removal system that offloads microscopic bits of fat and other matter. The sweat from the apocrine glands is the big problem with body odor. Bacteria feed on the fats and other secretions, and their waste products produce that distinctive fetid aroma that announces your presence before you enter a room. You'll notice after a vigorous workout that your sweat smells OK, not great, but at least clean and healthy. Wait a couple of hours and the bacterial feeding frenzy that ensues will transform your healthy smelling sweat into something pretty foul.
The strength of the odor a person produces depends on how much sweat his or her glands secrete as well as the number of bacteria on the skin. People with strong underarm odors carry two to three times as much underarm bacteria as other people. The best way to prevent body odor is to wash away sweat and bacteria thoroughly and regularly. Clean the underarm and groin area with water and soap, preferably a deodorant soap, at least once a day and more often if necessary.