We all have body odor; that's just life. But what is it, exactly? Why does one person's B.O. smell different or worse than another's? It's a complicated topic, but here's a crash course in everything you've ever wanted to know (and some things you never wanted to learn) about body odor.

What is body odor?

Body odor is caused by bacteria that naturally live on the skin's surface. Your sweat consists of different types of acids and other chemicals. When this sweat hits the skin, the bacteria have a feeding frenzy as they break down the acids in your sweat.

If you wanna get more scientific, here you go: You have two types of sweat glands, eccrine and apocrine. Eccrine glands are all over the body, and they tend to produce sweat that is more water than anything else. The bacteria on your skin ignore these glands for the most part.

Apocrine glands, meanwhile, are the ones located in areas like the underarms and the groin. Not only are they more or less useless in terms of cooling you off (which is the whole point of sweating in the first place), but they also release proteins and lipids called thioalcohols that create a tasty buffet for bacteria. As the chemicals are broken down, they release not-so-pleasant smells that can range from oniony and garlicky to meaty.

In 2009, a study conducted at National Human Genome Research Institute in Maryland discovered there are about 1,000 unique species of bacteria living on our skin. Another study at the University of York in England in 2015 found that the worst offender is a bacterium called Staphylococcus hominis. S. hominis, though harmless, has a voracious appetite and produces a lot of the thioalcohols we associate with bad B.O.

Does B.O. differ from person to person?

To put it simply, yes. But why? If these bacteria live on everyone's skin, why does one person's B.O. smell different (sometimes dramatically different) from another's? There are several reasons, actually:


You might not be what you eat, but you can certainly smell like it. Take red meat, for example. It's hard for our bodies to digest, which is why residues can be left behind. These residues are released with sweat. When hungry bacteria show up and break the odor-concealing protein shells, that smell gets released.

Oh, and if you chase that steak with a few beers, you're only making matters worse. Alcohol metabolizes into acetic acid, which is also released through the pores with sweat. So you might end up stinking of poorly digested steak and the cheap beer you had the night before. Sounds great, huh?

Other dietary staples that can worsen smelly sweat include cruciferous vegetables like broccoli and cabbage, and spices like garlic, onions, and curry, all of which contain sulfur that can make your sweat smell terrible. Some people have an inherited genetic issue called trimethylaminuria, which is a long name for the inability to properly digest and metabolize fish. As a result, their sweat can take on a fishy odor.

Bathing and Clothing

This should be obvious, but bathing daily will help keep B.O. to a minimum by rinsing away sweat and depriving bacteria of their food source. For added protection, you can use an antibacterial soap to kill bacteria (or at least keep them from multiplying so quickly).

Clothing also has a big effect. Breathable fabric like cotton is not only less likely to make you overheat and sweat more, but it also retains fewer of the chemicals that produce B.O. By comparison, polyester tends to not only cause more sweating but also traps the smelly chemicals, which sometimes can stick around even after washing.

Body Hair

Whether or not body hair actually worsens B.O. has never been proven conclusively. However, we do know that body hair is a good insulator, so areas in which it's very dense can be prone to sweating more. Underarm hair can lead to warmer temperatures, which means you'll sweat more easily and provide an even better breeding ground for bacteria. Shaving underarm hair reduces the warm, damp area in which bacteria can thrive. The sweat molecules will also have less to cling to and be easier to wash away when bathing.

Anxiety vs. "Normal" Sweat:

Remember the two kinds of sweat glands? Well, the difference explains why some types of sweat seem worse than others. The sweat you experience during a hard workout is not the same (nor will it smell the same) as the nervous sweat you experience just before a big event. Exercise and warm temperatures tend to make you sweat all over, although it's common to sweat more in some places than in others. Those eccrine glands found all over the body don't usually have pungent odors associated with them, as that sweat is primarily made up of water.

Anxiety-driven sweating, on the other hand, tends to occur where there are many apocrine glands, such as the armpits and groin. Unfortunately, these are the glands that secrete smelly compounds that bacteria love to break down into thioalcohols, which is what gives you that distinctive funk.

The Takeaway

So what can you learn from all this? Well, first, you're going to sweat. That's just part of life. Second, some of that sweat is going to smell. But if you limit unhealthy food, wear loose-fitting natural fibers, and bathe regularly (and maybe consider shaving your underarms), you can greatly reduce the smells emitted when you do sweat. The people around you will thank you for it.