system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come armpits and feet have their own unique bad scent? (onions vs Fritos chips?)
gpt
The armpits have what are called apocrine glands.  These are special scent/sweat glands which have a high protein output. Bacteria thrive here, breaking down this protein, creating one type of body odor. 

Feet do not have this type of gland, but due to wearing shoes and socks, the warm sweat sits there, and sits there, and sits there. This is also a very bacteria friendly environment, but the bacteria that thrive in this condition are feasting on a totally different diet, making a totally different smell.