Young Kissing Girls

Diseases which may be transmitted through kissing include mononucleosis, allergic reactions to nuts and drugs, and herpes, when the infectious virus is present in saliva. Research indicates that contraction of HIV via kissing is extremely unlikely, although a woman has been infected with HIV by kissing (in 1997). Both the woman and infected man had gum disease, so transmission was through the man's blood, not through saliva.
Health benefits
Affection in general has stress-reducing effects. Kissing in particular has been studied in a controlled experiment: increasing the frequency of kissing in marital and cohabiting relationships was found to result in a reduction of perceived stress, an increase in relationship satisfaction, and a lowering of cholesterol levels. Kissing can also cause the adrenal glands to release epinephorine and norepinephorine (adrenaline and noradrenaline) into the blood, thereby causing an adrenaline rush. It is beneficial to your cardiovascular health when the heart pumps faster. In an experiment by Dr. Alexander DeWees, a passionate kiss generally burns up to 2-3 calories per minute.