Thick saliva occurs when the body has a hard time producing enough of it, which is often a side effect of prescription and over-the-counter drugs, according to Medical Daily. The most common types of medications that produce thick saliva are for allergy, cold and pain.
Radiation therapy and chemotherapy treatments both cause thick saliva, states the American Cancer Society. Smoking cigarettes causes phlegm and excess mucus secretions, states Buddy MD. People who have low blood sugar due to untreated diabetes often experience thick saliva.
An excess buildup of thick, acidic saliva can break down tooth enamel and create cavities, according to Buddy MD. Brushing often and rinsing the mouth out helps reduce acid levels. Also, drinking plenty of water throughout the day thins mucus, states the American Cancer Society.