What Causes Underarm Odor?

Underarm odor is caused by bacteria that live on the skin and feed on sweat. When these bacteria break down sweat, they release an unpleasant smell. The amount of sweat produced and the type of bacteria present can both contribute to underarm odor.

Sweat Production

The body produces two types of sweat: eccrine and apocrine. Eccrine sweat is mostly water and salt, while apocrine sweat contains proteins and fatty acids. Apocrine sweat is produced in the armpits, groin, and other areas with many hair follicles. This type of sweat is more likely to cause body odor because it provides a food source for bacteria.


The type of bacteria present on the skin can also affect underarm odor. Staphylococcus epidermidis and Corynebacterium are two common types of bacteria found in the armpits. These bacteria feed on apocrine sweat and produce compounds that have a strong odor. Some people may be more prone to body odor due to differences in their bacterial populations.

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