What causes cats to drool?

According to Pet MD, cats drool due to stimulation of the salivary nuclei in the brain stem. Taste and touch sensations that involve the mouth and tongue, such as eating and drinking, also stimulate the production of extra saliva.

Drooling in cats can also be caused by structural disorders of the cat's lips, oral and pharyngeal diseases and diseases of the salivary glands. Esophageal or gastrointestinal disorders, metabolic and neurologic disorders and drugs and toxins are other causes. Drool is also caused by the higher centers of the central nervous system and lesions existing within the central nervous system or the oral cavity.