The 36-year-old actor insists it is his worst nightmare having to make out with someone else for a movie as he has had a phobia of germs since he was a young boy.
He said: "I'm also a germaphobe. I've been profoundly germaphobic since I was a young child. I don't want to kiss anyone but my girlfriend [Morgana McNelis] for my whole life."
Explaining why he is a germaphobe, he recalled to the latest issue of ELLE magazine: "When I was maybe eight or nine, there was a parasite from dogs in the north of England that, if you ingested it, could turn you blind.
"We had a thing in schools to educate the kids about the importance of hygiene, specifically around dogs, because we had a few kids who went blind. That horrified me. The point is, everyone thinks it's great to be an actor and get to kiss a bunch of beautiful actresses in films, but I actually hate it."
Meanwhile, Charlie previously gushed about his girlfriend and confessed he would like to get married and have children with her in the near future.
He said: "I have an incredibly understanding girlfriend who is requiring more and more as we get older that I figure out a way to balance these things a little better. I've gotten off pretty easily so far, with being able to just disappear and be completely selfish and singular in my focus, but if we're going to start talking about having children and getting married then I'm going to have to figure out a way to balance that a little bit more effectively."