Causes of Excessive Saliva in the Mouth

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Normal saliva production in the mouth varies from 1 to 2 liters per day. It is high just before and during eating and becomes low during sleep. About 0.5 milliliters of saliva is secreted every minute.

Saliva is mainly composed of mucus when not eating or if not stimulated by the sight, thought, taste and smell of food. This is secreted in small amounts by the buccal glands lining the mouth cavity and the sublingual and submandibular glands. 

When stimulated by the presence of food in the mouth, thought of food or other sensory perceptions, saliva production increases some 20-fold. The parotid, submandibular and sublingual glands produce large amounts of serous fluid containing the enzyme ptyalin which plays a part in carbohydrate digestion. Mucus production is also increased to lubricate the food and assist with swallowing.

Causes of saliva secretion 

Thought of foods that one finds tasty

Smelling, seeing or tasting delectable foods especially when hungry

Smooth objects in the mouth

Nervousness, anxiety, excitement

Chewing gum or tobacco, 

Teething

Pregnancy

Saliva Formation

Saliva is drained out of the mouth cavity by swallowing and it passes down the throat and esophagus and into the stomach. Two possible causes may result in hypersalivation :

Excessive saliva production (polysialia)

Inadequate drainage of saliva, often related to swallowing problems (more frequently dysphagia which is difficulty swallowing).

In most cases, excess saliva may be swallowed but if drooling is present, it may be an indication of difficulty swallowing.

Causes of Excessive Saliva in the Mouth

Orodental

Dental prosthetics – new and ill-fitting implants, bridges and dentures

TMJ dysfunction

Bruxism

Water brash

Esophagitis

GERD (gastroesophageal reflux disease)

Gastritis

Inflammation and Infection

Mouth inflammation (stomatitis)

Upper respiratory tract infections

Syphilis

Tuberculosis

Rabies

Encephalitis

Labyrinthitis

Pain

Any severe pain, especially if of sudden onset

Mouth pain (stomatodynia)

Nerve Disorders

Facial nerve – Bell’s palsy

Trigeminal neuralgia

Geniculate neuralgia

Medication and Illicit Substances:

Ketamines

Narcotics

Psychoactive drugs

Nicotine toxicity

Poisoning

Metal poisoning – mercury and arsenic poisoning being the most prominent.

Bites (insect, reptiles) – neurotoxic venom causes both dysphagia and hypersalivation

Mushroom poisoning

Medication that causes a dry mouth may result in hypersalivation when discontinued (rebound effect). However, in many cases, the restoration of normal salivary flow is initially mistaken for profuse salivation.