Drooling and Salivation

Role of Saliva in Digestion

Saliva, secreted primarily by the parotid, sublingual, and submandibular glands, along with smaller glands in the oral mucosa, produces about 1.5 liters daily. As part of the digestive system, saliva softens chewed food, forming a swallowable bolus. It dissolves food components, stimulating taste buds to trigger the production of other digestive juices in the stomach and intestines. Saliva also dilutes spicy, sour, or bitter foods and regulates food temperature. In omnivorous humans, saliva initiates carbohydrate breakdown via the enzyme ptyalin, which continues acting in the stomach. Unlike herbivores, which produce large amounts of saliva for prolonged chewing, carnivores rely less on saliva for digestion.

Saliva Production and Triggers

Saliva secretion is controlled by a brain center linked to the senses of smell and taste. Pleasant food aromas or flavors increase saliva production, while unappealing foods reduce it, making swallowing difficult. Saliva secretion can begin before food enters the mouth, triggered by the sight, smell, or even thought of appealing food. The most significant saliva production occurs during chewing and shortly after swallowing. Excessive salivation, or ptyalism, occurs when over two liters of saliva are produced daily without appropriate stimulation.

Salivation in Specific Groups

Newborns produce minimal saliva, with drooling typically starting after a few months as infants have not yet learned to swallow saliva effectively. Increased salivation in the 6th or 7th month often coincides with teething. In pregnancy, ptyalism is common, especially in the first trimester, usually resolving after two to three months. Severe cases can disrupt daily life, particularly when accompanied by vomiting, and are caused by nervous system irritation. Treatment may involve sedatives or secretion-reducing drugs, though salivation often stops abruptly on its own.

Causes of Excessive Salivation

In adults, diet influences salivation, with dry, spicy foods, smoking, dentures, or chewing gum increasing production. Nervous system irritation from discomfort, anger, fear, or hysterical episodes can also trigger excessive salivation. In hysteria, saliva is not swallowed but churned with air, creating a frothy, sticky appearance around the lips. Epileptics often drool during seizures, sometimes with blood due to tongue biting. Drooling in individuals with mental disabilities or post-brain disease is often "false salivation," resulting from an inability to swallow rather than excessive production. Neurological conditions like Parkinson’s disease cause continuous saliva leakage through a half-open mouth. Oral inflammation and poisoning from substances like mercury, nicotine, iodine, or pesticides also increase salivation.