Couples who share a passionate kiss this Valentine’s Day will enjoy sensations of relaxation and excitement because of a complex series of chemical processes, as well as their love for their partners.

The study showed that women need more than just a kiss to experience the same chemical high as men – with additional features such as a romantic atmosphere of dimmed lights and mood music also required.

Wendy Hill, professor of psychology at Lafayette College, Pennsylvania began the research to find out why the mundane physical activity of rubbing lips can elicit such a gratifying emotional response.

Her team tested the levels of two hormones, cortisol and oxytocin, in 15 couples before and after holding hands and kissing.

They found that kissing reduced the levels of cortisol, a stress hormone, in both sexes. But levels of oxytocin, a hormone linked to social bonding that they expected to be boosted by kissing, only rose among the men.