Gastroesophageal Reflux Disease (GERD): This condition is common in young adults and can cause excessive salivation due to the body's attempt to neutralize stomach acid. The symptoms can be exacerbated by eating certain foods, lying down after meals, or other factors that increase pressure on the lower esophageal sphincter.

Dental Problems: Issues such as gum disease, tooth decay, or poorly fitting dentures can cause discomfort that leads to increased salivation.
Anxiety or Stress: Psychological factors can influence salivary gland function, leading to excessive salivation in some individuals.
Medication Side Effects: Certain medications, including anticholinesterases, can increase salivation as a side effect.

Rabies: Although rare, rabies is a deadly viral disease that can present with excessive salivation among other symptoms like fever, agitation, and hydrophobia. Early diagnosis is crucial for treatment.
Tetanus: This bacterial infection can cause muscle stiffness and spasms, including those of the jaw and facial muscles, potentially leading to excessive salivation.
Neurological Disorders: Conditions such as Parkinson's disease or cerebral palsy can affect the autonomic nervous system, leading to abnormal salivation patterns.

Sjögren's Syndrome: An autoimmune disorder that primarily affects the glands that produce tears and saliva, leading to dry mouth and eyes, but can occasionally present with excessive salivation in its early stages.
Hypothyroidism: In some cases, hypothyroidism can lead to increased salivation, though this is less common and usually accompanied by other symptoms like weight gain, fatigue, and cold intolerance.
Pregnancy: Though the patient is male, in the context of considering all possible rare causes, pregnancy in females can lead to various oral changes, including increased salivation, due to hormonal fluctuations.