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According to the Mayo Clinic, the average person produces up to two quarts of saliva every day. This seemingly large amount of liquid in the mouth goes unnoticed most of the time due to the constant swallowing that most people are able to accomplish. Salivary gland disorders or other medical conditions that prevent frequent swallowing may cause a person to have excessive amounts of saliva in her mouth. Excessive salivation is referred to as sialorrhea and may stem from a variety of causes.

Exposure to Toxins

Exposure to high levels of toxins, including insecticides and mercury, can adversely affect the body. One of the side effects of such exposure is sialorrhea.

Medication Use

The use of medications, such as clozapine, a drug used to treat dementia, may cause abnormal salivation and lead to drooling. Medical researchers at Massachusetts General Hospital report in the June 2005 issue of "Drugs of Today" that some antibiotics and a medication called yohimbine may produce similar results.

Nerve Damage

People who suffer from Parkinson's disease, or other conditions that lead to nerve damage, may experience drooling and excessive saliva in the mouth.

Pregnancy

Pregnant women are likely to experience excessive saliva, according to the Mayo Clinic. Though the condition of producing more saliva than normal may be difficult to adjust to, it should not be a matter of concern for most people.

Dental Appliances

Being fitted for new braces, retainers or dentures may cause a person to produce more saliva. Dental health professionals may monitor the condition and assess if treatment is required, according to the American Academy of Family Physicians.

GERD

Gastroesophageal reflux disease (GERD) can be a cause of excessive saliva. GERD does not necessarily lead to overproduction of saliva, but may interfere with the swallowing process, according to the Mayo Clinic.