What makes for a really good kiss? Is it practice makes perfect, a romantic date night setting or a seductive red lip? Mood lighting and Kylie Jenner lips may boost your odds of getting that first kiss, but when it comes to being memorable, you’re gonna need some friends on your side. Little friends. Millions and millions of little friends. We’re talking microbes, people. Microbiologist Jason Tetro, author of The Germ Code, got real with us about the science of kissing. It ain’t pretty — you’re gonna want to grab some mouthwash, pronto — but it does explain why some sparks fly and others fizzle.

What That Bacteria in Your Mouth Is Up To


Before we can talk kissing techniques, we need to establish what’s going on in your mouth. It is FULL of bacteria, good and bad. “Bacteria love to eat, like us, and of course, once they are done they have to get rid of the waste,” says Jason. “So, when these bacteria are ejecting waste, it goes straight into your body.” And that’s why your breath stinks even when you don’t order the onion bagel. “Some of these waste molecules are quite smelly; they are known as volatile sulfur compounds and are responsible for bad breath.”

What Happens When You Kiss


Now for that classic romantic movie moment. At the end of the date, he walks you to your door like a perfect gentleman, leans in and… TRANSFERS 80 MILLION BACTERIA INTO YOUR MOUTH. Yup, Jason says that all it takes is a 10-second kiss to share that much bacteria. In fact, you can actually change the microbial communities in your partner’s mouth by kissing at least nine times a day for 10 seconds at a time. That’s if you’re full-on making out, though; it’s a lot less if you’re keeping it PG. “Bacteria transfer in our saliva, and any exchange involving the liquid will mean microbial sharing,” says Jason. “A peck will lead to little to no sharing, while a gentle kiss might transfer a few thousand bacteria. If you go right in for a deep kiss, you’re going to spread millions.”

How That Kiss Affects Your Relationship


Forget about your stars aligning — how do your microbial communities work together? “Bad breath has been shown to be a deal breaker for up to seven out of 10 people, says Jason. “If one of you has those sulfur-forming bacteria on your tongue, you may not be compatible with each other. On the other hand, if the bacteria on the tongue are neutral or even sweet, compatibility can be increased.” Also, if you’re experiencing dry mouth, you may want to reschedule your first date. “Lack of saliva is an indicator of stress and a leading factor in why people decided not to pursue a relationship.”

4 Tips to Pucker Up like a Pro


Did you ever imagine your germs could be such a deal breaker? Well, fear not, because Jason also offered some expert tips to keep that bacteria count down and increase your odds at a great first impression. (And no, practicing on your hand is NOT one of them.)

1. Brush, floss and go to the dentist. This one may seem like a big DUH, but don’t underestimate the power of good oral hygiene. Jason says it helps your odds tremendously. Freshen up your mouth before you head out, and if you’re facing any bigger problems like halitosis (aka bad breath), see your dentist for treatment.

2. Chew sugarless gum. “A simple two-minute chew can remove a hundred million bacteria, leaving you with fresh breath and little worry for any sulfuric consequences.” Just don’t snap your gum in front of your date — manners still apply.

3. Drink a liquid probiotic. Probiotics are live microorganisms that are known to improve your health. For example, Jason serves on the advisory board for Bio-K+ probiotics, which contain Lactobacillus rhamnosus and Lactobacillus casei, two good strains for stopping the nasty bacteria from forming sulfur. “You can coat the tongue and let those bacteria settle, giving you a little more confidence each and every day as well as when it comes to that first kiss,” says Jason.

4. Don’t stress. Like we said earlier, lack of saliva can be a major turn-off to some, and stress is a common cause of it. So kick those first-date jitters if you can. “After all,” says Jason, “if that first taste is dry and unfavorable, no matter how good a kisser you might be, it’s probably not going to get very far.”

Care to share your best and worst kiss stories? Dish in the comments!

(Photos via Getty)