Fresh sweat usually does not smell very strong.
The odor most people associate with sweating appears mainly after bacteria on the skin get involved.
That is especially true in places such as the armpits.
Your body has different kinds of sweat glands
Eccrine sweat glands are spread across much of the body.
They release the watery sweat used heavily for cooling.
Another type, called apocrine glands, is concentrated in areas such as the armpits and groin.
Their secretions contain more proteins and fats.
Bacteria break those substances down
Skin bacteria use some of the compounds in sweat and gland secretions.
As bacteria break them apart, smaller chemicals are produced.
Some of those chemicals have strong odors.
That is where much of familiar body odor comes from.
Why do two people smell different?
Everyone has a different mix of skin microbes.
Genetics, hormones, diet, medications, hygiene, clothing, and the amount of sweating can all affect odor.
Two people can sweat similar amounts and smell completely different.
Does all sweat smell bad?
No.
Sweat itself may have very little odor when it first reaches the skin.
Odor builds as microbes process substances on the skin.
That is why washing can make such a large difference even if the body starts sweating again later.
What is the difference between deodorant and antiperspirant?
Deodorant is aimed mainly at odor.
It may reduce odor-producing bacteria, cover smell, or do both.
Antiperspirant is designed to reduce the amount of sweat reaching the skin.
Products often combine both functions.
Why do feet smell too?
Feet contain many sweat glands and spend long periods in warm, enclosed shoes.
That creates excellent conditions for bacteria.
The basic biology is similar, even though the exact odor compounds can differ.
So sweat does not come out of your body already smelling like a locker room.
The bacteria provide the finishing service.
A related explanation is Why do we sweat?, which looks at another familiar effect from the same general system.
And that’s the short explanation.
Related explanations: Why do we sweat?, Why do feet smell?, and Why does your breath smell worse in the morning?