Drooling During Sleep: Causes and What to Do

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This article provides general information. If drooling is new, excessive, or accompanied by difficulty swallowing, slurred speech, or facial asymmetry, consult a physician promptly as these may indicate a medical condition requiring assessment.

Why Drooling Happens During Sleep

The body produces 0.75 to 1.5 litres of saliva per day. During waking hours, we swallow reflexively and continuously, typically 500-700 times per day, which keeps saliva from pooling. During sleep, two things change: first, swallowing frequency drops significantly (though it doesn't stop entirely); second, muscle tone throughout the body relaxes, including the muscles that keep the lips sealed and the soft palate positioned to close off the throat.

When sleeping in a lateral position (side) or prone position (stomach), gravity pulls the relaxed jaw slightly open. Saliva that accumulates in the mouth pools toward the lower side and can flow out if the lips are not fully sealed. This is the basic mechanism behind most benign sleep drooling: gravity plus reduced swallowing plus muscle relaxation. It is not a sign of anything wrong with your body.

Common Causes of Drooling in Sleep

1. Sleep position: Side and stomach sleepers are significantly more likely to drool than back sleepers. Back sleeping keeps the mouth directed upward, allowing saliva to drain toward the throat for swallowing rather than pooling at the lips.

2. Nasal congestion and mouth breathing: When the nasal airway is blocked by congestion (from allergies, a cold, sinusitis, or a deviated septum), breathing switches to the mouth during sleep. Mouth breathing requires keeping the mouth open, which creates a direct exit route for saliva. Seasonal allergy sufferers often notice increased drooling during high pollen periods. Addressing the nasal obstruction typically resolves the drooling.

3. Medications: Several categories of medication increase saliva production (sialorrhoea) or reduce the muscle tone and swallowing reflexes that normally manage saliva. This is among the more significant causes of clinically notable drooling in adults. (See the medications section below.)

4. Sleep apnea: People with obstructive sleep apnea tend to breathe through their mouths and may have more pronounced muscle relaxation in the throat and jaw area, both of which contribute to drooling. Drooling is not a diagnostic sign for sleep apnea but is associated with it in some patients.

5. GERD (gastroesophageal reflux): Acid reflux can stimulate the salivary glands through a reflex mechanism (waterbrash), increasing saliva production specifically when reflux occurs. Nighttime GERD is associated with increased drooling episodes, usually accompanied by the characteristic acid taste in the mouth or burning sensation.

6. Pregnancy: Hypersalivation (excessive saliva production) is a recognised symptom in the first trimester, often accompanying morning sickness (nausea gravidarum). The mechanism is not fully understood but may involve hormonal effects on salivary gland activity. It typically resolves as the first trimester ends.

7. Neurological conditions: Less commonly, drooling during sleep can indicate reduced swallowing coordination from neurological causes. Parkinson's disease, ALS (amyotrophic lateral sclerosis), cerebral palsy, and post-stroke swallowing difficulties all affect the reflexive saliva management. In these cases, daytime drooling is typically also present.

Sleep Position and Drooling

For people whose drooling is purely positional and benign, the simplest approach is adjusting sleep position toward back sleeping. This is easier said than done for habitual side or stomach sleepers, but the following approaches help:

• Elevated head: Sleeping with the head slightly elevated (either through a wedge pillow or by raising the head of the bed) reduces the pooling tendency even for side sleepers. An elevation of 10-15 degrees is generally sufficient without causing neck discomfort.
• Pillow selection: For side sleepers, a pillow that keeps the head in neutral alignment rather than tilted back (which opens the mouth) or too far forward (which compresses the jaw) helps maintain a more natural lip seal. A slightly firmer pillow that doesn't compress excessively under head weight tends to work better for this.
• Back sleeping training: Using a body pillow on each side, or the "tennis ball in the shirt back" technique, can discourage rolling to the side during sleep over time.

Medications That Cause Drooling

If drooling is new or has worsened, a medication review is worthwhile. The following categories are commonly associated with increased drooling:

If a medication you've recently started is causing drooling, do not stop it without first speaking to your prescribing physician or pharmacist. Many of these medications have important therapeutic roles, and there may be dosing adjustments, timing changes, or alternative medications that reduce the side effect while maintaining therapeutic benefit.

When to See a Doctor

Most sleep drooling is benign and requires no medical attention. See a physician if:

• Drooling during sleep is a new symptom that has appeared suddenly without a clear cause (new medication, new nasal congestion)
• It is accompanied by difficulty swallowing food or liquids during waking hours
• It is accompanied by changes in speech (slurring, weakening voice)
• There is facial asymmetry, weakness on one side of the face, or the drooling is occurring from one side only
• The drooling is severe enough to cause skin breakdown or repeated aspiration

The combination of new-onset drooling with facial asymmetry or speech changes can indicate stroke and warrants immediate medical assessment, not a scheduled appointment.

Practical Solutions for Drooling

• Treat nasal congestion: Saline rinse before bed, nasal corticosteroid spray for chronic allergies (fluticasone, budesonide), air purifier to reduce allergen load in the bedroom. If a deviated septum is suspected, ENT referral.
• Adjust sleep position: Try back sleeping with the head slightly elevated. A wedge pillow (10-15 degrees) helps both position and potential GERD.
• Pillow protector: A waterproof mattress protector and a washable pillow protector are practical hygiene solutions for regular side sleepers who drool. They protect the pillow fill (particularly foam or latex pillows that don't wash well) and are far cheaper than replacing pillows frequently.
• Review medications with your pharmacist: If a medication is the suspected cause, a pharmacist can review whether timing adjustments (taking the medication earlier in the day) or alternatives exist.
• Chin strap: For persistent mouth opening during sleep without obstructive sleep apnea, a chin strap may help maintain lip seal. The evidence is limited and comfort is variable, but it is a low-risk option.

Related Reading

• Anti-Snoring Solutions: Mouthguards, Strips and Devices
• Insomnia Symptoms and Natural Treatment Guide
• Sleep Inertia: Why You Feel Groggy After Waking
• Magnesium for Sleep: Does It Work and How Much to Take?

Sources

• Leibowitz, M.R. (2012). Nocturnal sialorrhoea: causes, assessment and management. Sleep Medicine Clinics, 7(3), 457–467.
• Bavikatte, G., et al. (2012). Approach to drooling in neurological conditions: a clinical review. Therapeutic Advances in Neurological Disorders, 5(2), 111–118.
• Meningaud, J.P., et al. (2006). Drooling of saliva: a review of the etiology and management options. Oral Surgery, Oral Medicine, Oral Pathology, 101(1), 48–57.
• Dawes, C. (2008). Salivary flow patterns and the health of hard and soft oral tissues. Journal of the American Dental Association, 139 Suppl, 18S–24S.
• Health Canada. (2022). Managing medication side effects. canada.ca