Herpes can only be passed through direct skin-to-skin contact with the infected area such as kissing, oral sex, genital-to-genital rubbing, vaginal, and anal sex. Herpes (both oral & genital) can be spread even when there are no symptoms or sores.
Yes, you can catch herpes just from kissing someone on the mouth. And while experts believe the risk of catching HIV (the virus that causes AIDS) from kissing is low, someone who has a cut or sore in the mouth has a chance of infection during open-mouthed kissing.