Every Bad Smell Your Body Makes, Explained

From bad breath to bad gas, here's the science behind every stinky smell your body makes.

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The human body: A work of art, a wonder of nature, a miracle of perfect engineering. Also, a revolting sack of churning goo and miscellaneous stench. Yes, even people with perfect bodies are susceptible to all the various gross forms of body odor that plague us regular folk. But what is it that makes us all so, well, stinky?

The short answer is bacteria: Your body is covered in bacteria, which feeds on everything from your shedding skin cells to the food in your intestines—what you can smell is actually the byproduct of their digestion. But in that case, why are all the smells so different? Let’s find out, working our way from head to toe…

Your Breath

“Up to 10% of many populations will have chronic halitosis,” says Dr. George Preti, a research scientist who studies human secretions and odors at the Monell Chemical Senses Center. “It’s a condition caused by bacteria that builds up on the posterior dorsal surface of the tongue, and it’s very hard to get rid of—you have to keep your tongue clean. I’ve seen some people complaining of bad odor from their mouth, and the back of their tongue looks like it’s got cream cheese on it. That’s how bad the plaque is.”

Your Armpits

“Bacteria thrive in moist conditions, and because the armpits are covered up, there’s more moisture there since it’s not as likely to evaporate,” says Preti. “Because of that level of wetness, there are greater levels of what’s called coryneform bacteria. These have been closely associated with the formation of underarm odor.” Your armpits also contain apocrine glands—the glands that produce that oily, smelly form of sweat you secrete when stressed. All in all, your armpits are a tiny, stinky nightmare factory.

Your Groin

“Your groin also has apocrine glands, but it doesn’t smell like an armpit because it doesn’t have the same bacterial population,” explains Preti. “Your pubic area is much dryer than your armpits, so the resident bacteria is different.” Your groin also shares an abundance of staphylococcus bacteria with your pits and feet. “These are on all parts of your skin, but they’re present in greater numbers in these areas because there’s more moisture,” says Preti.

Your Gas

As with body odor, gas is actually caused by bacteria metabolizing stuff—in this case, the food in your gut. According to gastroenterologist Satish S.C. Rao, different types of food cause different smells. Brussels sprouts, for example, contain sulfur, which causes your gas to smell like rotten eggs, while those with lactose intolerance will find any kind of dairy causes their gas to smell even worse than normal. Why did you think it was called cutting the cheese?

Your Feet

“People with very smelly feet often have a build up of certain types of bacteria,” says Preti. “There’s a particular condition called pitted keratolysis that causes a lot of skin exfoliation. This will lead to a greater bacteria build up because there are more skin cells for them to metabolize material from, and so a greater level of odor is produced.” In other words, the more your skin peels down there, the more bacteria show up to snack on that delicious foot flake buffet.