Ever Wonder Why Your Body Stinks?

There is one word that sums up what is responsible for 90 percent of the bad smells that come from the human body—bacteria. If you haven’t learned about these creatures yet, bacterial are living things that are so small you can’t see them without a powerful microscope.

Most bacteria are either harmless or even helpful in some way. For example, koalas would not be able to digest eucalyptus leaves if not for the bacteria living in their intestinal tract. This is so important that when baby koalas are six months old, they begin feeding on something called pap in addition to nursing. Pap is a special type of feces (poop) that a mother koala excretes for her baby. It contains protein and lots of bacteria that the joey will need once it starts eating eucalyptus leaves.

As far as humans go, there are more bacteria living on (and in) our bodies than there are people on the earth. In fact, it is estimated that each of us carts around about a trillion of them. And where, you might ask, do these bacteria “settle down” to live? Everywhere!

Even though we don’t eat eucalyptus leaves, the bacteria in our intestines help us digest our food. These bacteria also release waste products that give poop its awful smell.

Bacteria also cause bad breath and smelly skin. The reason your breath smells better after you brush your teeth or your armpits smell better after you shower is because you have washed away billions of bacteria—and their gross byproducts.

Most bacteria like moisture, so sweat plays an important role in how people smell. We have two kinds of sweat glands in our bodies. Eccrine glands, work at all ages. Apocrine glands don’t start working until a person enters puberty. The types of bacteria that produce raunchy body odor love to feast on the sweat produced by apocrine glands. This explains why a 14-year-old has the potential to smell much worse than an 8-year-old.

Bacteria reproduce very fast. That’s why you can brush your teeth at night and wake up with stinky breath eight hours later. While you slept, the bacteria in your mouth grew up, got married and had lots of babies. Actually, bacteria don’t really get married. In fact, they don’t even need other bacteria to reproduce. They multiply by a process called asexual reproduction, which is something you will learn about in middle school.

Kids dislike cleaning anything (including themselves), which is why your parents are always bugging you to do it. So the next time you’re inclined to put off some personal hygiene, think of it as a search and destroy mission to wipe out the microscopic invaders that are all over your body.

First Published in the Washington Post, December 15, 2008