What causes excessive salivation?

Causes of Excessive Salivation

Excessive salivation (hypersalivation or sialorrhea) is most commonly caused by poor oral and facial muscle control in neurologically impaired individuals, but can also result from medication side effects, certain neurological conditions, and dysphagia. 1, 2

Neurological and Anatomical Causes

• Neurological disorders are primary causes of hypersalivation, including Parkinson's disease, stroke, cerebral palsy, and other conditions that affect oro-motor function and coordination 2, 3
• Dysphagia (swallowing difficulty) can lead to apparent hypersalivation due to reduced clearance rather than increased production, particularly in patients with neurological disorders such as Parkinson's disease and post-stroke conditions 4
• Insufficient oro-motor function and decreased central control of swallowing mechanisms are key factors in excessive salivation 3
• Hypotonic oral muscles, particularly in children, can lead to poor lip closure and subsequent drooling 1

Medication-Related Causes

• Acetylcholinesterase (AChE) inhibitors used for symptomatic treatment of Alzheimer's disease are a common cause of increased saliva production 4
• Clozapine and other antipsychotics are strongly associated with clinically significant drooling 5
• Direct and indirect cholinergic agonists used to treat dementia and myasthenia gravis can cause hypersalivation 5
• Certain medications can cause cholinergic overstimulation, leading to excessive secretory gland activity including salivation 4

Other Medical Conditions

• Oral and gum diseases can contribute to excessive salivation 4
• Chronic kidney disease (CKD) can cause salivary disorders, including altered salivary composition that may affect flow and consistency 4
• Exposure to heavy metal toxins (mercury and thallium) and irreversible acetylcholinesterase inhibitors (insecticides and nerve agents) can induce drooling 5
• Irritation from certain antibiotics and other medications that affect the oral mucosa can increase salivation 5

Contributing Factors

• Age-related changes: While aging typically results in lower salivary flow rates, certain age-related conditions can paradoxically present with excessive salivation 4
• Food and drink consumption: Acidic foods stimulate saliva production more than sugar or carbohydrate-rich foods 4
• Physical and psychological stressors can impact salivary flow and composition 4
• Dental malocclusion and postural problems can contribute to apparent drooling by affecting the ability to contain saliva in the mouth 2

Pathophysiological Mechanisms

• Hypersalivation can occur through two primary mechanisms:
  1. Increased production of saliva beyond what can be managed by normal swallowing 2, 5
  2. Normal or even reduced saliva production with impaired swallowing function 2, 5
• Muscarinic receptor overstimulation leads to increased activity of secretory glands, including salivary glands 4
• In some cases, particularly with dysphagia, the appearance of excessive salivation may be due to pooling rather than overproduction 4

Clinical Implications

• Excessive salivation can cause perioral chapping, dehydration, odor, and social stigmatization 2
• In patients with swallowing disorders, pooled saliva increases the risk of aspiration 3
• Proper diagnosis should differentiate between true hypersalivation (increased production) and apparent hypersalivation due to impaired clearance 4
• Treatment approaches vary based on the underlying cause and may include medications (anticholinergics like glycopyrrolate), botulinum toxin injections, or surgical interventions in severe cases 6, 2, 3

Understanding the specific cause of excessive salivation is essential for appropriate management, as treatment strategies differ significantly depending on whether the problem is due to overproduction or impaired clearance of saliva.