So far, we’ve skirted over one nagging question—namely, why does your personal air conditioner smell like dirty socks? Surprisingly, sweat itself has no odor. You can douse yourself in the stuff without picking up the faintest scent. However, the bacteria that live on your skin aren’t so innocent—they feed on your sweat and produce a rich collection of stinky substances. (This is the reason a discarded workout shirt smells worse the next day—the bacteria living on it have had some extra time to digest its tasty payload.)
As you’ve probably noticed, body odor seems to emanate from specific places in your body. To understand why, you need to recognize that your body actually has two types of sweat gland:
• Eccrine. These are the most numerous sweat glands. They’re found all over your body and are particularly dense on the palms of your hands, the soles of your feet, and on your forehead. The eccrine glands do most of your body’s temperature control.
• Apocrine. These sweat glands are concentrated in the forested areas— the armpits and genitals. Instead of secreting ordinary salt water, they squirt out a thick, milky fluid that has plenty of fats and proteins.
Apocrine glands almost always dump their contents onto a hair follicle. Unlike eccrine sweat glands, apocrine glands don’t do much for temperature control, and they react more readily to emotions and sexual stimulation. Bacteria devour rich, apocrine sweat, leaving their signature gamey odors behind. Bacteria aren’t nearly as interested in the watery sweat that leaks out of the eccrine glands, but under the right conditions they can still make a meal of it, along with skin oils and dead skin cells. (That’s why a warm, moist, poorly ventilated foot can develop a room-clearing odor that rivals the sweatiest armpit.)
This raises an excellent question—if apocrine glands don’t help you cool your body, why are they there stinking up the place? It seems that the chief purpose of apocrine sweat is to create your distinctive body odor. Several studies have shown that women, when asked to smell a lineup of used undershirts, can pick out their man’s shirt by smell. Thus, apocrine glands are the human equivalent of the sexual-scent glands of other animals— and whether they have a real effect or are just an evolutionary leftover depends on whom you ask.
Apocrine glands develop during puberty, which is why babies and toddlers don’t have body odor problems.
Source of Information : Oreilly - Your Body Missing Manual