Drooling while sleeping is a common and usually harmless phenomenon. It often occurs simply because of how the body relaxes during sleep.

One main cause is muscle relaxation. During deep sleep phases like REM, facial and jaw muscles loosen, allowing the mouth to open slightly and saliva to escape.

Sleeping position also affects drooling. People who sleep on their stomach or side tend to drool more since gravity pulls saliva out, while sleeping on the back typically reduces it.

Nasal congestion from allergies or colds can force someone to breathe through their mouth, increasing the chance of drooling during sleep.

Some individuals experience hypersalivation, or excessive saliva production, due to infections, swollen tonsils, or reactions to medications or certain foods.

Gastroesophageal reflux disease (GERD) can also cause increased saliva flow, leading to drooling at night.

In more serious cases, neurological disorders such as Parkinson’s disease or stroke can impair muscle control and swallowing, resulting in drooling. Some medications, including sedatives and antipsychotics, may have similar effects.

If drooling is excessive, frequent, or comes with breathing problems or loud snoring, it’s wise to see a doctor. Simple remedies like sleeping on your back, managing congestion, and practicing good oral hygiene can help reduce nighttime drooling.