1. Normal physiological process.

Saliva production is a natural bodily function that helps keep your mouth moist. During sleep, the muscles in your mouth and throat relax, which can lead to increased saliva production. This excess saliva may accumulate and drool onto your pillow.

2. Sleep position.

The position in which you sleep can affect saliva flow. Sleeping on your side or stomach can allow saliva to escape from your mouth, leading to drooling. Gravity also plays a role, as saliva tends to pool and trickle downwards while lying down.

3. Sleeping disorders.

Certain sleep disorders like sleep apnea can cause changes in saliva production and control. Sleep apnea is characterized by pauses in breathing during sleep, leading to mouth dryness followed by excessive saliva production when breathing resumes. This can result in drooling during sleep.

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