Hi, my 3 year old cannot keep his tongue in his mouth. He is constantly leaving it out, licking the lower lip area. His chin area is ends up always wet which makes him lick even more because he says he is trying to lick his saliva up.

So you are saying that he cannot or doesn't want to put his tongue inside his mouth? If he cannot, best to see a doctor or a dentist to see if anything can be done about his tongue situation. If he doesn't want to because of all the saliva like he said, you can also ask the doctor why is he drooling so much, might be a gum inflammation. Here is an informative article about the possible reasons for your child's tongue protrusion.