Do you sometimes wake up with drool on your pillow? Just how normal is this — and is there anything you can do about it?

Saliva is one of your body's unsung heroes. It helps you taste and swallow food, protects your teeth from decay, and helps keep harmful pathogens in check. "Without saliva, we are in trouble," says one dental expert.

Every day, you produce about 0.5 to 1.5 litres of saliva, and drooling is simply what happens when it escapes your mouth. This is generally normal, but understanding how and why you drool can help you avoid some awkward, uncomfortable moments.

What causes drooling?

Most of the time, drooling happens because saliva builds up faster than you can get rid of it. During the day, you usually manage saliva by swallowing. But while asleep, you swallow less often and have less conscious control over the muscles around your mouth.

Breathing through your mouth makes drooling even more likely because saliva has an easier exit. If you sleep on your side or stomach — or you nod off while sitting, like on a bus or train — gravity can also work against you.

Children also tend to drool more than adults. Babies and toddlers are still developing control of their lips, tongue, jaw, and swallowing muscles, while teething can stimulate extra saliva, helping soothe tender gums. Young children also explore the world with their mouths — sucking on thumbs, chewing on toys, or sitting with their mouths open — which can increase drooling. For most children, this improves as those muscles and swallowing patterns mature, usually by around age 4.

What can you do to reduce drooling?

Changing sleep positions can help with drooling at night. Sleeping on your back is not ideal for people with sleep apnoea, but it is usually the best position to reduce drooling. If you tend to roll around and have trouble staying on your back, placing pillows around your body can act like bumpers, keeping you in place.

Addressing congestion may also help. Treating allergies or a cold can make it easier to breathe through your nose and potentially reduce drooling. Nasal strips might also help, but experts recommend avoiding mouth tape, since that can just make it harder to breathe.

You may also want to avoid food and drinks that stimulate saliva before bed. Anything sour can get your salivary glands going, as can sugary food and drinks — though to a lesser extent. Acid reflux can have a similar effect, so avoid eating too close to bedtime and steer clear of spicy or greasy foods. If you wear Invisalign, a retainer, or another dental device at night, try not to grind your teeth, since that kind of mechanical stimulation also increases saliva production.

Should you talk to your doctor?

In general, nighttime drooling is common and usually not a cause for concern. But drooling during the day is a little more worrisome, and you should see a doctor if it abruptly worsens or feels excessive, since that might be a sign of a more serious condition.

For example, drooling can sometimes point to sleep apnoea or a structural problem that makes it hard to breathe through the nose. In children, this may be enlarged tonsils or adenoids that block the airway. In adults, loose or fatty tissue in the back of the throat can have a similar effect.

Drooling can also stem from genetic and neurological conditions that affect muscle control or swallowing, such as cerebral palsy, Down syndrome, Parkinson's disease, dementia, ALS, or a stroke.

The right approach for excess drooling depends on the cause. If it is related to an airway problem, something like a tonsillectomy or using a continuous positive airway pressure (CPAP) machine can help. Some patients also benefit from swallowing exercises or mouth therapy to strengthen coordination of the lips, tongue, and muscles.

In more severe cases, doctors may prescribe medications to dry the mouth, inject Botox into the salivary glands to temporarily reduce activity, or perform surgery. These approaches tend to be used cautiously because drying out the mouth too much can be uncomfortable. "Making too little saliva is a bigger problem than making too much," one expert notes.

The bottom line

A damp pillow might be embarrassing, but it is nothing to lose sleep over. "It is more of a nuisance than an emergency," says one sleep specialist. For most people, small adjustments — like changing sleep position, managing congestion, and avoiding certain foods before bed — can make a noticeable difference.