What Causes Body Odor? And Other Stinky Questions, Answered

what causes body odor

It’s a classic nightmare scenario: you walk into a room full of people having lively, fun-filled conversations. Slowly, all conversation stalls and heads turn, delicately sniffing the air. “What’s that smell?” someone wonders aloud, wrinkling her nose. You inconspicuously tilt your nose towards your underarm and do the classic sniff test—and OH NO, that stink is coming from you.

Okay, so hopefully this hypothetical situation hasn’t *actually* happened to you (not if you’re wearing your trusty aluminum-free deodorant, anyway). But you probably know that feeling of dread that comes with wondering if you’ve got B.O., a.k.a. body odor. 

But what actually causes that unmistakable smell, and how can you prevent bad body odor in your life? You’ve got questions, we’ve got answers.

First, what causes body odor? 

Body odor is caused by your bacteria breaking down sweat into certain acids. Sweat, on its own, is totally odorless; the smell comes from certain strains of bacteria that live under your arms and how those bacteria mix with your sweat. Some people naturally have more bacteria in that area, and so they might be more susceptible to a little funk. 

Your microbiome is unique to you, and bacteria is a natural, essential part of a healthy microbiome—so you never want to sterilize and eliminate your microbiome altogether. Still, sometimes that bacteria can get out of whack. Your personal hygiene mission, then, is to find products that support the right balance of bacteria for your body’s chemistry, while reducing the bacteria that thrive a little too much in moist, odor-causing environments.

Can stress cause body odor?

Surprisingly enough, it can. Your body has two types of sweat glands: eccrine glands and apocrine glands. Eccrine glands are located all over your body, especially in your palms and the soles of your feet. The water-based secretion that comes out of them is used mostly for cooling your body off, which is especially helpful during a hot yoga class

Apocrine glands, meanwhile, are mostly concentrated in your underarm and groin area—the areas of your body that are most prone to B.O. These glands expel sweat that’s filled with protein and fats, which causes a more pungent smell. When you start to panic over that upcoming work presentation, your apocrine glands fire up, and the stress sweat mingling with your underarm bacteria is what causes our most pungent body odor.

Can diet affect body odor?

It’s possible! If you’re the person always bringing their own hot sauce to the party, just beware: spicy foods, as well as foods topped with garlic, curry, and other spices, release sulfur-containing gasses that can linger in your pores for hours after your meal. 

Similarly, a sweet tooth could be to blame for B.O. Eating a ton of sugar makes your body over-produce yeast, which transforms sugars into alcohols and contributes to a bad smell. 

Does body odor have a purpose? 

Yup, that unpleasant smell that happens when you forget your clean deodorant for a day has an evolutionary function. Mothers can identify their natural-born children by smell, and babies can recognize their mothers by smell, too. In general, personal smell is a huge identifier in both the human and animal worlds. But unless you’re playing a really strange game at a family reunion, chances are bad body odor doesn’t have a major function in your life. 

How can I prevent body odor?

Your best defense against body odor is preventing it in the first place, rather than trying to freshen up after the B.O. has already reared its ugly head. Using an effective, non-toxic deodorant on a daily basis is the best way to prevent body odor. 

Don’t forget, you’ll want to apply your deo to clean, dry skin for best results; starting with a dry surface ensures that your deodorant only powers on when you start to sweat, and being so fresh and so clean means that nothing comes in between you and your deodorant. If your deodorant isn’t working, try changing how you apply deodorant, taking a look at your diet, or going for an unscented deodorant. 

So the next time you find yourself in a hot, crowded room, don’t be afraid to wave enthusiastically to a friend, gesture wildly to emphasize a story you’re telling, or even do the YMCA. With a clean, powerful deodorant by your side (er, under your arms), you’re free from body odor and the mortification that comes with wondering whether you’re the source of that weird smell.

Now that you know what causes body odor, we've got the best way for you to fight it. 


Written by Kristen Geil