So one of our readers asked us this question the other day: Why does armpits sweat smell significantly worse than sweat from other body parts?
The human body has 2 types of sweat glands. The first type is called an eccrine sweat gland. These are located all over the body and produce mostly watery sweat. The other kind is called apocrine sweat glands. Apocrine sweat glands are found in the armpits and groin areas. Apocrine glands make sweat that has more protein and other nutrients than sweat from eccrine sweat glands.
There’re bacteria in your armpits that digests these minerals in your sweat and produces volatile (smelly) compounds as a waste product. This is deliberate. Your body produces and secretes some of those chemicals on purpose, to feed those bacteria. Those chemicals aren’t present before puberty, mostly, which is why children don’t smell bad, but teens smell awful. Exactly why that happens, no one is entirely sure.
One theory is that it’s probably something to do with attracting a mate. The strong scent would indicate that the person has extra resources to waste on feeding unnecessary bacteria. It smells bad now because we have germ theory and hygiene. Our fitness is demonstrated by our cleanliness now. Technology and culture has changed faster than evolution.
Another theory is that before mammals had developed nipples and dedicated mammary glands to provide milk, some mammals just secreted milky sweat that was enriched with fats and protein from certain patches of skin, in order to feed their young. The echidna is one of the few animals that still does this. Though the thought of nursing your children on underarm or groin sweat is disgusting, the apocrine glands are still producing an “enriched sweat” that may have originally been used for that very purpose.