1. Sleep Position
When you sleep at night, your mouth produces extra saliva to help protect your gums and the inside of your mouth. The muscles of your body also relax during sleep, including those of your face and jaw. If you sleep on your side or stomach, drooling may be more likely to occur as excess saliva escapes from the sides of your mouth. This is more likely to happen if your nose is more stuffed up, because you will subconsciously sleep with your mouth slightly open in order to breathe better during the night. For this reason, you may notice you drool only during an allergy flare-up or when you have a cold.