On the face of it, kissing seems like a strange thing for humans to do. One theory is that it stems from mothers weaning their children in early societies – our ancient ancestors might have pre-chewed food for babies and transferred it directly to their mouths, as chimpanzees do.

But it seems historians don’t know exactly when or how kissing progressed into a way to show romantic interest or love – or why we even do it.

What we do know though is that it feels good, which may be down to the many mental and physiological benefits.

“Kissing is about giving yourself up and offering yourself to somebody else,” explains Dr Sandra Wheatley, a social psychologist with a special interest in relationships. “You’re exposing yourself, because it’s also got potentially negative consequences like cold sores and catching infections,  but your reward is that someone else feels the same about you.

“This makes you feel like you’re a good judge of character, and all the hope you have, and alleviation of the potential fear that you’ve got the signals wrong, will give you a buzz chemically.”

Here’s why kissing is so good for you…

1.  It produces feel-good hormones

Research shows kissing stimulates the brain to produce a cocktail of chemicals including oxytocin, dopamine, and serotonin, which can make you feel good and encourage feelings of affection and bonding.

2. Kissing helps reduce blood pressure

The arousal of kissing someone increases your heart rate, which dilates blood vessels, leading to an increase in blood flow and a consequent drop in blood pressure, according to Andrea Demirjian, author of Kissing: Everything You Ever Wanted to Know About One of Life’s Sweetest Pleasures.

Psychologist Dr Audrey Tang of the British Psychological Society (bps.org.uk) says: “In the book Demirjian talks about how, physiologically, kissing can help blood vessel dilation – which in turn means a lowering of blood pressure because of the improved blood flow, Indeed, research supports this with kissing being related to a drop in cortisol levels (reducing stress) as well as a rise in oxytocin, the bonding hormone.

“This in turn brings psychological benefits – not only do we feel good, but we also know we can be safe with the person we’re kissing, and in turn this can boost our sense of security in part because of the awareness that we’re not alone.”

3. Kissing reduces stress

A study by researchers at Arizona State University found kissing is linked to lower stress levels and lower cholesterol levels, and more research from Lafayette College in the US found levels of cortisol,  the stress hormone, dropped for both men and women after kissing.

Wheatley thinks the reason for this is easy to understand. “Kissing can be de-stressing, which I think is part of the confirmation that you were right, and the person you’re kissing thinks you’re just as great as you think they are.”

4. It’s a confidence booster

It’s not hard to see why somebody kissing you can make you feel good, and not just because of the hormones it releases. Wheatley says: “It boosts your self-esteem – and we all need a bit of that – because a kiss suggests the person you’re kissing finds you as attractive as you find them.”

5. It gives your face a workout

Although a simple peck isn’t going to work many of your facial muscles,  the American cardiologist Dr Joseph Alpert, writing in the American Journal of Medicine,  suggests a passionate kiss can activate up to 24 facial muscles and 112 postural muscles.

“Kissing can give your facial muscles a workout as well as burn some calories,” says Tang, “so the benefits are physical as well as physiological and psychological!”

6. Kissing is a useful ‘mate assessment’ tool

Tang explains that research shows kissing is particularly useful for women to work out the relationship suitability of the person they’re kissing. She says: “Interestingly, a study found kissing can indeed work as a useful mate-assessment function for a significant number of women, who stated that an initial kiss was more likely to affect their attraction to a potential mate.  They also found that kissing was seen as important in long-term relationships, and kissing frequency was linked to relationship satisfaction.”

7. It helps people bond

Kissing isn’t always sexual, of course, and even pecks on the cheeks of family and friends can help them bond, Tang points out. “It’s not just intimate and sexual relationships that benefit – kissing family members is also a tangible expression of bonding, and releases oxytocin, and again this can improve trust and connection, reducing fear of facing a challenging world alone.”