Why We Drool in Our Sleep

Nasal Congestion and Difficulty Swallowing May Contribute to a Wet Pillow


It may seem a little embarrassing: you wake up and your pillow is drenched in slobber. After you wipe the spit at the corners of your mouth, you might wonder: Why do we drool in our sleep? Learn about some of the most common causes of drooling in sleep and what you can do about it.

Reasons Drooling Happens While Asleep

The body normally produces more than 1 liter of saliva per day. It is produced by salivary glands and is usually swallowed and re-circulated via the bloodstream.

Drooling occurs when the saliva collects within the mouth and rather than being swallowed, it drips or runs out past the lips. Why might this occur more at night?

The simplest answer is that you drool during sleep because your mouth is open. The muscles of the body relax during sleep, especially during REM sleep, and it is possible for your mouth to fall open at this time. Some suggest that sleep position may matter, and that sleeping on your side may make it more likely to leak saliva rather than swallowing it.

One of the biggest reasons your mouth could come open at night is because you can’t breathe well through your nose. We are meant to breathe through our nose, but if congestion is present, our default option is to breathe through the mouth. If this occurs in sleep, saliva may drool onto our pillow. Nasal congestion may occur with a cold or secondary to allergies like hay fever. In addition, a deviated nasal septum may block the nose and contribute to mouth breathing.

As a result of this obstruction, both snoring and sleep apnea may be associated with drooling.

In addition, excessive salivation (sialorrhea) may occur due to the use of medications or other medical conditions. It may be associated with difficulty swallowing that occurs secondary to a brain injury, stroke, or even Parkinson’s disease.

This will often manifest during the daytime as well. It may also be associated with gastroesophageal reflux disease (GERD) or heartburn at night.

What to Do: Treatment Options for Drooling in Sleep

In general, it is not necessary to treat drooling in sleep in isolation. If it occurs rarely, it may be annoying, but does not require treatment. It won’t lead to dehydration, infection, or other problems. It may be helpful to treat nasal congestion if this is present. If other symptoms of sleep apnea are present, evaluation for this condition may help with nighttime breathing and drooling. When secondary to other medical conditions that impair swallowing, prescription medications such as atropine drops or scopolamine patches are sometimes used.

If you are concerned about chronic drooling on your pillow, speak with your doctor to see if you need further evaluation and treatment.


Kryger, MH et al. "Principles and Practice of Sleep Medicine." Elsevier, 5th edition, 2011.

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