Does Saliva Have Health Risks? 3 Ways Germs Can Spread

Find out which viruses and bacteria can become someone else's problem
Toothbrushes in close proximity

Your mouth is home to hundreds of different microorganisms. What happens when you’re exposed to someone else’s saliva?

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There are ways in which saliva can serve as an important defense for our bodies, says Michael Benninger, MD. “Saliva has antibodies and enzymes that decrease the risk of contagions.”

Still, there are plenty of ways to transmit certain illnesses via saliva, an issue that’s getting new attention thanks to the outbreak of the novel COVID-19 coronavirus.

Saliva is a large focus on helping prevent the spread of coronavirus. “There is clearly coronavirus in saliva,” says Dr. Benninger, “so anything like sharing food is a high-risk contact and should be avoided.”

Here are a few other illnesses which can work their way from your saliva into your nose, throat and lungs:

  • Rhinovirus (colds).
  • Flu virus.
  • Epstein-Barr virus (mononucleosis, or mono).
  • Type 1 herpes (cold sores).
  • Strep bacteria.
  • Hepatitis B and hepatitis C.
  • Cytomegalovirus (a risk during fetal development).

Other new viruses, such as ebola virus and bird flu, are also a concern. Dr. Benninger says. Contrary to popular belief, however, the AIDS virus (human immunodeficiency virus, or HIV) is not transmitted through saliva.

Here are four ways you can accidentally transmit infection through saliva.


It’s easy to exchange infectious organisms during a kiss through your saliva. They can find their way from your mouth into your throat and lungs. (That’s why mono is called the “kissing disease.”)

That’s what’s particularly important to keep physical safeguards in mind during the COVID-19 outbreak. “If someone’s a health care worker and they may have had exposure to the coronavirus, they should even avoid kissing their spouse,” says Dr. Benninger.

Other viruses, like colds and flu, can also be spread by kissing, although cold viruses usually spread by touching a contaminated surface and then your nose, says Dr. Benninger.

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Your saliva typically protects you against bacteria in your partner’s saliva. (There will be more bacteria when oral hygiene is poor.) But one bacteria that can be transmitted is MRSA, the serious staph infection.

Also, if you have a cold sore, kissing someone can spread the herpes 1 virus. “Despite this, there is lots of kissing going on, and very few infections,” says Dr. Benninger.


While most people don’t think of saliva when they think of sneezing, it’s actually an important component especially in these days of social distancing.

When a person sneezes, the sudden, powerful expulsion of air can propel mucous droplets at rates of up to 100 miles per hour. Likewise, saliva droplets can also be propelled several feet away. If you’re far enough away, Dr. Benninger notes, those virus-carrying droplets drop to the ground. 

But if you’re close enough to someone sneezing, it’s possible to get hit with those saliva droplets and expose yourself to the virus or another potential illness. It’s one reason why health professionals have recommended staying at least six feet away from others during the coronavirus outbreak.

Dr. Benninger notes it’s also one of the reasons why it’s so important to follow proper coughing and sneezing etiquette by covering your mouth.

Sharing toothbrushes + mouthguards

Ever forget a toothbrush and borrow your partner’s? The American Dental Association advises against this practice.

“Toothbrushes may cause microtrauma. Someone else’s saliva can come in contact with tears in your mucous membrane and transmit infection,” explains Dr. Benninger.

Sharing toothbrushes is especially risky if you have a weakened immune system.

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Have a cold, sore throat or other virus? Keep your toothbrush from touching the family toothpaste and others’ toothbrushes.

There are also several types of mouthguards — those that protect your teeth, mouth and jaw during sports, and help keep you from grinding your teeth at night.

You can get stock mouthguards from a sporting goods store, “bite and boil” mouthguards from a drugstore, or custom-made mouthguards from your dentist.

Whatever type you use, mouthguards, which are porous, should never be shared. A 2007 study, reported in General Dentistry, found that mouthguards harbor bacteria, yeasts and molds.

“Someone else’s mouthguard may fit very poorly and cause microtrauma,” says Dr. Benninger. This can expose your mucous membranes to infection.

If you wear a mouthguard, be sure to:

  • Brush your teeth before inserting it.
  • Clean it whenever you brush your teeth.
  • Store it in a case.
  • Avoid chewing on it.

The bottom line

Now, more than ever, it’s important to be smart about saliva and who you might be sharing it with. While it’s important to remember that “saliva has some wonderful things in it that helps protect us,” according to Dr. Benninger, it can also spread this new, challenging infectious disease. 

“Saliva is important for our teeth, it’s important for so many things,” he adds, “but at the same time, it’s also potentially contagious.”

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