According to the Mayo Clinic, excessive salivation is either caused by an increase in the body's production of saliva or a decrease in a person's ability to swallow or keep saliva in his mouth. There are multiple reasons why either situation can occur, including the development of an oral infection, the use of certain prescription medications or an overactive salivary gland.
According to WebMD, excessive salivation is typically not a cause for concern. However, if the problem persists, a health care provider can help determine its cause. Doctors might check to see if patients who salivate or drool excessively have poor facial muscle control or problems swallowing. Bell's palsy and Parkinson's disease can cause facial muscles to weaken, and esophageal atresia and stomatitis very often make swallowing difficult. All of these conditions can cause excessive salivation, according to the Mayo Clinic.
If doctors are able to rule out a medical condition, diet might be a contributing factor. Acidic foods and spicy foods can cause salivary glands to become overactive. Acid reflux disease can also lead to excessive drooling. WebMD notes that medications used to treat seizures and schizophrenia, such as clozapine and clonazepam, can also cause excessive salivation in adults.