As someone with immune issues and many friends who also deal with it, our favorite phrase in this situation is "is you getting a hug worth my death?" Pointing out the legit possible end result that you have to struggle with to someone who is all up in their own happy fluffy feelings is a rough play. But you need to sometimes.

As for the making out, spray bottle. If they want to act like puppies in heat, treat them like it. Or reminding them to save space for Jesus. Or that if they want a threesome, to call your husband. Because without him knowing and giving prior consent, it's cheating.