The science behind kissing: 10 things that happen when we kiss

Whether it’s a quick polite peck, or an awkwardly long PDA that spurs on a chorus of ‘Get a room’, there are several biological and chemical changes that happen inside us when we kiss- there is even a field of study dedicated to this – Philematology, which is the science of kissing.

People often say they can decide if there is ‘chemistry’ between you and a partner by one kiss – so here is the literal chemistry we all unknowingly refer to:

Can anyone else see the pheromones between them?
Can anyone else see the pheromones between them?

1. Kissing relieves stress:

Several studies have measured levels of the stress hormone, Cortisol, before and after a make out session, and in both men and women there is a consistent, significant drop in cortisol. So if you are stressed – have a little smooch (although if it is work related stress maybe don’t pucker up in the boardroom, that would be super awkward).

2. Kissing releases the love hormone – Oxytocin:

There is a reason Oxytocin is known as the love hormone – it is released from the pituitary gland when we engage in sexual activity. It has the effect of making us feel sexually aroused and can also makes us feel a closer bond and more trust with our partner. When we kiss our levels of Oxytocin sky rocket, so kissing does make us feel closer.

3. Men pass along their testosterone in saliva to activate women’s sex drives

An interesting theory by Helen Fisher from Rutger’s University found that there is testosterone present in men’s saliva. She also found that men preferred a more saliva filled, slobbery kiss. Her theory was that men were unconsciously passing their testosterone filled saliva on to women in an attempt to activate the part of the woman’s brain associated with sex drive. I think this idea is intriguing, it certainly makes evolutionary sense, though I’m not a fan of sloppy kisses myself!

4. All the happiness chemicals are released:

Kissing stimulates nerve endings on our lips, which sparks release of dopamine. Dopamine is a neurotransmitter that is active in circuits in the brain associated with pleasure, and it makes us feel happy. Dopamine is also associated with feeling rewarded, which can make us want to repeat a behaviour – so one kiss with someone really can lead you to wanting more of them. Endorphins are released when we kiss, these are neuropeptides that gives us a happy buzz, like after we exercise. Phenylethylamine levels also increase during a kiss, this chemical is actually similar to amphetamines, and it not only makes us happy, it has aphrodisiac effects too! Don’t worry if you don’t have a special someone to smooch, you can find phenyethylamines in chocolate!

5. Your adrenal system gets all excited

When we kiss the adrenal system releases adrenaline and noradrenaline. This puts our whole body into an excited, revved up state where our heart rate increases and sugars break down in the body to give us more energy so we are ready for action. Also, blood rushes away from the stomach to our muscles and our sexual organs, so we can be prepared for any impending…. further action….

6. You tone up your face muscles

You use about 30 muscles when you kiss (depending on the type of kiss) and repeatedly doing this can exercise these muscles in a way that tones up the muscles in your face, preventing them from drooping, so kissing can prolong your youthful looks.

7. Pheromones fly about between you

Pheromones are like hormones, but they are released outside of your body, and recognised by others of the same species. Nobody really understands them, but from what we know so far these chemicals are released when we kiss, and our partner can sense them with their nose and mouth and will be able to detect if you are aroused. This is much better documented in animals, but it is thought humans could act the same way.

8. You burn loads of calories:

Passionate kissing is said to burn 6.4 calories a minute. That means half an hour of kissing burns the same amount of calories as running for ¬†around 25 minutes or swimming for about 30 minutes (depending on how fat or fit you are). Would you rather go to the gym or get some ‘alternative exercise’? Let me think about that one.

9. The way you tilt your head is learnt in the womb.

We have all had the awkward situation where you both lean your head one way, and then you bash heads and it’s super awkward and kills the moment. Head orientation preference in kissing is actually thought to be developed when we are a foetus, due to where our head and hands are positioned in the womb. Now there isn’t a huge amount of evidence on this, but I think the idea of it is cute. Research has found that most people do tend to tilt to the right anyway, and that when there is a clash of heads it is a real turn off! (I know you are tilting your head whilst reading this, and I know most of you are tilting to the right!)

10. Our pupils widen:

This is why we¬†close our eyes when we kiss – it’s just creepy having big bug eyes staring at you!

So now we know that the little spark we feel in those tender moments is actually just a series of chemical reactions and our hormones flying about having a little party. It is thought however that these reactions don’t occur as strongly when the physical attraction isn’t there, so it is true that you can decide if there is real attraction and chemistry with just one kiss…

Till next time,




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Hi everyone!

Just a quick note to say that I have added my blog to Bloglovin, so you can keep up to date with all my brand new sparkly posts if you follow me on there!

Also, thought I would let you know, that coming soon on Sparkly Science is some more on hangover cures, a debate on using marijuana as a cancer cure, looking at the science behind good mascara, the science behind flirting and much more!

Till next time,