Generally there are two types of kissing. First light kissing and the other one is deep kissing also known as French kiss or smooch. Deep kissing is done with the mouth slightly open and with the tongue reaching into the opposite mouth.
Even casual and light kissing carries some risk to it, simply because it puts you in close, intimate contact with another person and you may fall sick being infected by all their germs.
Also, even light kissing carries a slight risk for catching Herpes and Scabies if kissing someone who has open sores or cuts immediately around their mouth.
Deep kissing carries the same risks as light kissing, plus the exchange of fluids (the spit-swapping) increases those risks. It also allows for other sexually transmitted diseases to pass, such as Herpes Simplex Virus-2, Hepatitis B and Syphilis. The trick to dramatically lowering your risks is to really know your partner well, to know their sexual history, and to know their current health status.
Agencies