When a man kisses a woman it is possible for her testosterone levels to be raised. This raises her receptivity and libido.
The word kiss is from the old English ‘cyssan’. This is from the proto-Germanic word ‘kussijanan’ stemming from the sound kissing makes.
Kissing increase levels of Oxytocin & Endorphins the body’s calming and feel good chemicals. It also increases dopamine, which assists with romantic attachment.