Do your feet reek after you take off your soccer cleats or basketball shoes? Do your dirty socks wrinkle noses? Do your slippers smell so bad, the family dog won’t even retrieve them anymore?
“Most of the odors that we make are due to microbes that grow on our skin,” explains Gavin Thomas, a biologist at the University of York in Britain.
It may be icky to think about microbes, or more specifically, bacteria, growing all over our bodies, but scientists say these microscopic critters are pretty much always there, and they usually do us no harm.
“There’s one particular bacterium called Staphylococcus epidermidis, which is all over the body,” says Thomas. “And that is able to eat things called amino acids.”
Now, just like you or me or the squirrel in the tree outside your window, after all those itty bitty bacteria eat something, they have to get rid of waste. And those waste products — bacteria poop — are what make your feet stink, says Thomas.
What’s even more interesting is that your body’s stink will actually start to change as you get older. This is because when our bodies go through puberty, a new kind of sweat gland turns on in places like the armpits. There are microbes living there, too, and once those new sweat glands turn on, the bacteria go to work gobbling up your body’s secretions and discharging smelly waste, too. This is also why stinky armpits smell totally different from stinky feet — different sweat, different microbes.
By the way, if you’re wondering why some parts of us are smellier than others, Thomas says you can think of the human body like a bunch of different ecosystems.
“The open skin is a bit like a desert, because it’s dry and you’ve got ultraviolet light,” like what comes from the sun, says Thomas. “It’s a pretty harsh environment to live in.”
On the other hand, armpits and feet are a little bit more like a jungle. They tend to be warm, moist and dark — all things that bacteria love.