The human body sweats for various reasons, including to lower body temperature in the heat, during exercise, fever, infection, etc. While sweat itself is odorless, it creates an unpleasant odor when it comes into contact with skin bacteria. The main culprits behind body odor are apocrine glands, which are found in areas like the armpits and groin.
Antiperspirants are applied to the underarms to reduce the amount of sweat produced by sweat glands and prevent odor. They create unfavourable conditions for the bacteria that create odor.
Antiperspirants work by blocking the eccrine sweat gland with a gel plug on the outer layer of the skin, thereby reducing the amount of sweat that reaches the surface of the skin. Since these processes occur on the level of the epidermis, these plugs are gradually repelled in the wake of the skin renewal with the keratinisation process.
In order to reduce body odor, antiperspirants are often applied in combination with deodorants impair the growth of bacteria. The most commonly used antiperspirants are aluminum compounds.