The Dirty Truth About Kissing

There's no doubt that kissing is a pretty fun activity, no matter who you are or what your relationship status is. When you're single, kissing someone new for the first time can feel like an explosion of fireworks and when you're in a relationship, a kiss can feel warm and comforting. Dating and relationship expert April Davis told Bustle, "When kissing, it should feel as if the two of you are focused on each other and the rest of the world blurs around you." Romantic, right? Not so fast. The truth about kissing is that it can be pretty dirty — and, uh, not in a fun way.

As it happens, half of the world's population thinks kissing is gross, according to a study cited by Medical Daily. And they're not exactly wrong. Kissing is pretty nasty, and it doesn't even take all that long for a make-out sesh to go from seriously romantic to seriously dangerous to your health. But there's more to swapping spit than you might think, even in terms of germs. So, if you want to know the whole messy truth about kissing, keep on reading.

Perhaps one of the most obvious downsides to kissing is that it can transfer germs between the two people locking lips. A 2014 study published in Microbiome Journal found that there was an "average total bacterial transfer of 80 million bacteria per intimate kiss of 10 [seconds]." Eek. Plus, Remco Kort, the study's author and a professor and scientist, told Time, "Apparently, being with somebody for an extended amount of time and having a relationship leads to a similar collection of bacteria on the tongue." The more you know, right?

Additionally, Kelly Reynolds, a microbiologist at the University of Arizona's Zuckerman College of Public Health, told Cosmopolitan, "Mouths can serve as a transmission route for germs because there is close connection with the gastrointestinal and respiratory systems, and these are common sites of infections for germs." It's pretty overwhelming to think about, but important to remember before you decide to move in on that hottie at the bar.

Kissing usually feels pretty good. After all, why would you press your mouth up against someone else's if it wasn't an enjoyable experience? Plus, there's actually some science that proves kissing is doing good for you as well.

Sarah Johns, an expert in human reproduction and evolutionary psychology at the University of Kent in England, told The Independent that kissing has historically served a biologically important purpose. "Humans don't have strong olfactory skills and kissing allows you to smell and taste a person and see if you have different immune responses as we tend to feel more attracted to someone with a different immune response," she explained. "By kissing and tasting someone it gives the opportunity to assess how similar or different that individual is to you biochemically," Johns added. As outlandish as it sounds, if you feel a bigger spark with one person over another while kissing, it might be biology telling you that you're more attracted to them.

It is scary knowing that kissing can transfer a ton of bacteria, but it's not all bad. Microbiologist Remco Kort told HuffPost, "If you increase the diversity of good bacteria, you can increase resistance against infection." So, in a way, kissing people can actually benefit your immune system by increasing the number of overall bacteria that enter into your body — even if some of them aren't the best.

When you've been with someone for an extended period of time, your immune system will benefit from all the kissing that goes on between the two of you, Kort explained in an interview with Time. This is because you build up a resistance when you are exposed to different kinds of bacteria. While you can look at kissing and cringe at all of the bad bacteria being exchanged, Kort explained, "If you look at it from this point of view, kissing is very healthy."

To avoid catching the flu or other illnesses, you know frequent hand washing is important. What you may not have considered, though, is how it's entirely possible to catch the flu through smooching. Interestingly, it turns out that having sex is actually safer than kissing when it comes to the flu.

Charles Gerba, a microbiology professor at the University of Arizona, told Vice that you can somewhat safely have sex while you have the flu. Of course, you may not actually be in the mood if you're sick, but we digress. Even if you choose to get intimate while you're battling the flu, though, you should plan to keep kissing off-limits. "If you kiss, you're going to get sick," Gerba said. "And we've found that the influenza virus can live for three days on the couch." AdvoCare likewise advises that you should watch out for "close contact" situations, one of which being, of course, kissing.

Kissing is certainly fun and exciting and a great way to check if you are sexually compatible with someone new. Additionally, kissing shows someone you love just how much you love them. And though kissing is obviously pretty germy, it can also add years onto your life.

Citing a decade-long German study, Time explained that "men who kissed their wives before leaving for work lived, on average, five years longer, earning 20 to 30 percent more than peers who left without a peck good-bye." Additionally, the research found that men who didn't kiss their wives before they left for work were 50 percent more likely to get into a car accident, thus obviously shortening their lifespan.

Since kissing a special someone can be both thrilling and comforting at the same time, it's not exactly surprising that it's been linked with longevity. Though, it may not have a ton to do with the kiss itself. "Psychologists do not believe it's the kiss itself that accounts for the difference but rather that kissers were likely to begin the day with a positive attitude, leading to a healthier lifestyle," Time continued. You might as well plop a kiss on your partner's lips every morning, germs be damned.

No one enjoys the company of cold sores. They are pretty much the definition of "small but mighty" in terms of pain and annoyance. Cold sores, or fever blisters are they are often called, aren't that big of a deal, but they are incredibly frustrating and can really put a damper on your confidence since they can be difficult to cover up.

Cold sores are caused by the herpes simplex virus and can be easily spread to others through kissing, especially if your cold sore blister has already formed or even erupted. Additionally, cold sores can even be spread after they've healed up.

"One of the most common ways the virus is spread is through kissing, because the virus frequently occurs around the mouth and the lips," Joshua Zeichner, a dermatologist based in New York City, told Abreva. If you've recently kissed someone who had a cold sore, you may not show symptoms right away, but you could still be contagious. Thus, it's a good idea to hold off on the lip-locking for a time.

It's pretty much an undisputed fact that no one enjoys going to the dentist. Sure, it's not the worst thing in the world, but it can be pretty stressful — even if you take excellent care of your teeth and gums. Plus, even if you are the most meticulous teeth-brusher and flosser in the world, you could still get cavities as a result of kissing, believe it or not.

The act of kissing alone doesn't immediately lead to cavities, but swapping saliva does have the potential to spread the bacteria that causes cavities. "Cavities are caused by bacteria that stick to teeth and feast on food particles and produce acid that causes tooth decay," dentist Emanuel Layliev of the New York Center for Cosmetic Dentistry told Self. "Cavities are typically passed through mouth-to-mouth contact when there is an exchange of saliva." So on top of all the germs that get passed around while kissing, there's also the possibility that you can get more cavities from tongue-tangling with someone. Fun times!

If you don a smartwatch or other kind of wearable device that can track your heartrate, you may have noticed that your heart rate tends to go up while you're getting it on with someone. Heck, your watch might even think you're working out instead of just hooking up. And, to be fair, kissing does burn calories. But does it actually burn enough calories to really even count? Well, it depends on the time and effort you put into it.

A 2013 editorial published in the American Journal of Medicine revealed, "Simple kisses use as few as 2 muscles and burn only 2 to 3 calories, whereas passionate kissing can involve as many as 23 to 34 facial muscles and 112 postural muscles." Because of that, "the act of kissing consumes between 5 and 26 calories per minute," the study concluded. That's some serious calorie-torching just for getting it on! Obviously, to really burn some calories you would have to make out for a while, but honestly, there are worse ways to break a sweat.

Hepatitis B is a liver disease that can lead to liver cancer, liver failure, and kidney disease, according to the Mayo Clinic. And, unfortunately, kissing is one way in which the disease can be transmitted.

According to the Better Health Channel, it is able to pass Hepatitis B through kissing, though the site revealed that blood is more often the culprit. Yet and still, you can become sick with hepatitis B if infected saliva comes into contact with your bloodstream or mucus membranes, like your mouth. It's easiest to pass hepatitis B through kissing when someone has open and active sores around or inside their mouth. It's important to take the necessary precautions if your partner has the disease so you can keep yourself safe and healthy. And in this case, prevention really is the best medicine. As the Mayo Clinic revealed, "A vaccine can prevent hepatitis B, but there's no cure if you have the condition."

As far as the world has come in regards to modern medicine, there are obviously still some diseases and illnesses that you want to be careful to avoid. Meningococcal meningitis, for example, is a disease you really don't want to mess around with. According to the World Health Organization, "Meningococcal meningitis, a bacterial form of meningitis, is a serious infection of the meninges that affects the brain membrane. It can cause severe brain damage and is fatal in 50% of cases if untreated."

What's more, the Centers for Disease Control and Prevention (CDC) reported one terrifying way this meningococcal disease is spread: sharing saliva. The CDC added that "it takes close (for example, coughing or kissing) or lengthy contact to spread these bacteria. However, meningococcal meningitis isn't very common in the United States. In fact, the rate of the disease have been on the decline since the '90s. Still, it's something to be aware of.

When you have a food allergy, you tend to be pretty diligent about what you eat — and even where you eat — to ensure you don't have a reaction. Even if your allergy isn't severe, though, you probably watch out for things that can trigger a reaction. But did you know that kissing can be one of those triggers? If you aren't careful, the person you lock lips with might end up giving you hives.

A 2003 study published in the Journal of Investigational Allergology and Clinical Immunology concluded: "What other people eat can influence the quality of life of food-allergic patients. And the study confirmed that kissing is one such way this happens. That's right, if you have a food allergy and kiss someone who has eaten something you're allergic to, you could have a severe allergic reaction.

According to the study, "12% of the patients experienced allergic symptoms when in close contact with (e.g., kissing) a person who had eaten a non tolerated food prior to the contact." If you have a food allergy, you're going to want to be extra cautious when sharing kisses.

Out of all the diseases that can be transmitted through kissing, you may not have pictured gingivitis. It seems odd that an oral mouth disease can be transferred from one person to the next, but the dirty truth about kissing is that it seemingly can lead to gum disease. However, this is only the case if you've been kissing someone who already has it.

According to Medicine Net, the bacteria that causes gingivitis, or gum disease, can be passed between people who share utensils, cups, water bottles, silverware, and yes, saliva. "Theoretically, it may be transmitted or spread by kissing," the publication explained. Nevertheless, this bacteria isn't the sole cause of gingivitis; dental health and diet play an important role.

If your partner or spouse has gum disease that doesn't mean you have to completely avoid getting intimate with them, just make sure to take good and proper care of your own oral health. That way, any germs that are transmitted won't stand a chance of causing gum disease.

When you were in high school or college, you were probably warned about mononucleosis, or mono as it is often called. The disease is a type of virus that has a lot of the same symptoms as the cold or flu, but tends to last a lot longer, according to the Mayo Clinic. Mono is also well-known for being easily transmitted through kissing. After all, there's a reason people tend to call it "the kissing disease."

While mono can be spread through coughing, sneezing, or sharing utensils, it's usually transmitted from saliva, according to the Mayo Clinic. Who knew something so horrifying could be lurking in that hot and steamy kiss? 

Mono is pretty common, though, and as the Mayo Clinic reported, it's generally not something to be too concerned with. However, if you develop symptoms of mononucleosis that last longer than two weeks, it's probably time to see a doctor and get it checked out.

It might sound obvious to say that kissing makes you feel good, but there's actually more truth to it than that. There are scientific reasons why kissing feels so great. And it has a whole lot to do with hormones.

According to Healthline, your lips are the part of your body with the most nerve endings, so the actual physical touch of a kiss truly does make you feel amazing. Then there's also the feel-good chemicals released during kissing. A 2013 study found that the chemical oxytocin, a hormone released during kissing, helps men to feel a strong connection with their partner and means they will be more likely to stay loyal and monogamous to that person.

Additionally, another study published in the Articles of Sexual Behavior published that same year found a relationship between "kissing frequency" and "relationship satisfaction." The more smooching, the higher the relationship satisfaction. Kissing is a sure-fire way to feel great and increase your happiness, even if it is arguably pretty dirty.