Is it safe to kiss someone if you don't know if they have mouth herpes? what are some symptoms to know for sure if they do?

Now way to know: You can get oral transmission of herpes if you have contact with a carrier that has active virus shedding. This occurs when the person has an active herpetic lesion (usually looks like an open sore or a small clear blister). Unfortunately, the viral shedding starts before the lesion appears. Usually the carrier can tell he is going to have an outbreak, but you can't tell by looking at him.