How risky is kissing?

No one has ever caught HIV from kissing, no matter how hard they went for it, so allow yourself to get passionate and smoochy. Although very small quantities of HIV have been detected in saliva, your spit also has properties that disable HIV so it would be impossible to swallow enough saliva to become infected with HIV. And anyway, when people talk about the potential risk of catching HIV from saliva they say that you'd have to drink pints of it, which would be extremely hard to do (see how long it takes you to fill even a small glass if you don't believe us).

You can pick up herpes and glandular fever from kissing though, so it's probably best to avoid snogging anyone with visible cold sores around their mouth.