Why do i drool in my sleep? did it when i was little and now again.

Breathe through nose: Try breathing through your nose. Many people drool when they sleep because they're breathing through their mouths. If your nose gets stuffy, perhaps you are suffering from air-borne allergies or food sensitivities, causing a mild inflammatory response and therefore stuffiness. If you can breathe through your nose and keep your mouth closed, your saliva will stay in your mouth--and you won't snore!

Mouthbreathing: You might be sleeping with your mouth open. If you have developed nasal obstruction, this will cause you to sleep with your mouth open and subsequently drool.