First impressions are very important. Whether it's a first date or a job interview, you want to possess an air of confidence, smell nice and flash a great smile. Brushing your teeth will keep those pearly whites gleaming, but did you know that brushing your tongue is just as important?

The human mouth is its own ecosystem, with over six hundred different microbes calling it home. Most of these microbes are bacteria, and while some of the bacteria are good for us, some of them are bad. Good bacteria are called commensals. Commensals do not cause disease and co-exist with us in peace. They grow in thin layers, called biofilms, over the surfaces in our mouths to prevent the bad, disease-causing, bacteria from growing there. People who brush their teeth and floss regularly have healthy mouths with a normal balance of commensals versus disease-causing bacteria. People who aren't so good at keeping their mouths healthy may have problems like tooth decay, plaque and bad breath.

Did You Know?
The Human Microbiome Project is aiming to characterize every single microbe living in or on the human body. One of the areas they are focusing on is the mouth. Their goal is to determine how the population of bacteria inside the mouth changes with disease.

Tooth decay and plaque is caused by a bacterium called Streptococcus, which lives on your teeth. Every time you eat something with sugar in it, the Streptococcus are eating too. They use sugar to grow, which results in the production of lactic acid and some super sticky glucans, otherwise known as plaque. Plaque helps trap the acid against the tooth, which is what causes tooth decay. Since all of this is happening right on the surface of the teeth, all you have to do to prevent tooth decay is to brush your teeth and floss!

Bad breath (halitosis) is another story, and this story begins on the tongue. To bacteria, the tongue is an attractive place to live. It's warm and moist, like a giant sponge, and there's no shortage of food; every time you eat, pieces of food get trapped on your tongue. The tongue attracts a balance of commensal and disease-causing bacteria. This balance usually contains a lot more commensal bacteria, and very little bad bacteria. When this balance changes for the worse, the disease-causing bacteria will start to grow. These bad bacteria can produce smelly sulphur (rotten egg smelling) compounds right on your tongue, causing bad breath. The easiest way to control bad breath is to brush your tongue. Tongue brushing helps to get rid of a lot of the bacteria on your tongue, which leads to better smelling breath.

Did You Know?
Tongue cleaning has been practiced all throughout history. Ancient Chinese and Indian civilizations practised tongue scraping, and tongue scrapers made of bone, ivory and tortoise shell have been found dating back to the 1800's.

There are other ways of controlling bad breath, like mouthwashes, and chewing gum, but save your money because these things only hide the bad breath smell, replacing them with more pleasant ones. In fact, rinsing with mouthwash may actually make bad breath worse! Mouthwash is designed to kill almost all of the bacteria in your mouth, even the commensals. But after an hour or two, everything grows back (good and bad), and the bad breath returns as well. Mouthwash also contains alcohols, which dries out the mouth. This prevents our saliva (spit) from doing its job of washing the mouth and the bacteria grow back unchecked. Chewing gum does increase the flow of saliva in the mouth, but it doesn't get rid of enough bacteria.

Did You Know?
Effective tongue cleaning only requires brushing with a toothbrush or gentle scraping with a spoon. There's no need to buy a special tongue scraper from the drugstore!

So the next time you need to make a good first impression, don't forget to brush your tongue. When it comes down to it, it just feels good to have clean teeth and fresh breath.


Pennisi, E. A mouthful of microbes (2005) Science 307: 1899-1901.

Danser MM, Gómez SM, Van der Weijden GA. Tongue coating and tongue brushing: a literature review (2003) Int J Dent Hyg 1(3):151-8.

Human Microbiome Project

Nancy is working on her PhD at the University of Toronto, studying how the sexually transmitted infection gonorrhea affects the immune system. When she's not in the lab, she is probably playing ultimate frisbee.


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