Scientists believe that acid reflux episodes cause the gastric acid to stimulate the esophagus, as a result, the esophagosalivary reflex gets excited leading to excessive saliva production.
A sinus infection may be another cause for drooling. Upper respiratory tract infections are usually associated with breathing and swallowing problems, which cause drooling due to the accumulation of saliva.
Also, when your nasal passage is blocked due to flu, you tend to breathe with your mouth, which causes the excess saliva to flow out while sleeping.
You may suffer from sleep apnea. Symptoms of sleep apnea are difficulty sleeping, heavy breathing, loud snoring, or heavy drooling. If you have these symptoms, is better to consult the doctor.
How to prevent drooling on your pillow?
Try sleeping on your back. If you sleep on side, you are more prone to drooling during the night. This is simply because gravity is causing the mouth to open and allowing drool to pool on your pillow.
Breathe throw your nose. One of the main reason for drooling is that nasal sinuses are clogged. Because of this, people breathe throw their mouth and drooling in the process.