Dear Dr. Universe: Why do we get morning breath? — Stephanie, 10

Dear Stephanie,

If you’ve ever caught a whiff of someone’s stinky morning breath, or even your own, you know it can be pretty rotten. We can trace the smell back to tiny culprits that live in our mouths. They are called microbes and they live around your gums, between your teeth and on your tongue.

“They like to eat what you eat,” said my friend Claire Burbick, a veterinarian and microbiologist at Washington State University.

The microbes feed on leftover bits of food in your mouth. They not only help break down your food, but they also get energy from it. As they eat, grow and multiply, they also release some smelly gases that might remind you of rotten eggs.

When microbes eat foods rich in protein, such as meat or dairy, they tend to grow and multiply pretty fast, Burbick said. In fact, sometimes meat eaters get more stinky breath than plant eaters. Something else that adds to the stink is leftover food. If large pieces or food are stuck between teeth or in your gums, it becomes a kind of playground where microbes can grow.

The mouth can get kind of gross, but it also has a way to clean itself out. One way it does this is with saliva, or your spit. It’s mostly made out of water and contains a few chemicals that help fight off bad bacteria. Saliva is kind of like a built-in cleaning system. Of course, it isn’t perfect, so brushing your teeth also helps. Not to mention, your family and friends will thank you for it.

Whether snoring or just breathing deeply, animals and humans sometimes sleep with their mouths open. When air moves in, it can dry out the saliva in your mouth and create an environment that makes the stinky bacteria go wild.

In the morning, you might wake up with particularly bad breath. You’ll probably want to brush your teeth again, sending those stinky microbes down the drain and leaving your breath fresh.

Bad breath isn’t just a people problem, either. Cats, horses, cows and of course dogs get bad breath for many of the same reasons. Brushing teeth is also recommended for your pets, and they even have their own special toothpaste, said Burbick.

It turns out humans have been battling bad breath for thousands of years — and they’ve come up with some creative ideas. Some researchers have found evidence that ancient Egyptians mixed together spices and honey to create a kind of breath freshener. They also used thin twigs with frayed edges to scrub their teeth.

One of the first toothbrushes in human history was made in China. It had bristles made of hog hair and inspired the plastic toothbrushes humans use today. Humans also use floss, which helps get rid of bacteria in places where a toothbrush might not be able to reach. There’s also gum and mouthwash to help mask morning breath — or garlic breath, or onion breath, or whatever kind of stinky breath might come your way.

Sincerely,

Dr. Universe

“Ask Dr. Universe” is a science-education project based out of Washington State University. Send questions to Dr.Universe@wsu.edu.