Disease
Sjogren's Syndrome is a major cause of dry mouth.
Other disorders can also cause dry mouth or affect the salivary glands. Some people feel a dry mouth even if their salvary glands are working correctly. Some with certain diseases, like Parkinson's disease or those who have suffered a stroke, may not be able to feel wetness in their mouth and may think their mouth is dry even though it is not.
Side Effects of Some Medicines
More than 400 medicines can cause the salivary glands to make less saliva. However, do not stop taking them without asking your doctor, your dose may have already have been adjusted to help protect you against drying side effects or chosen a drug that's least likely to cause dryness. These medications include:
Radiation therapy
The salivary glands can be damaged if they are exposed to radiation during cancer treatment.
Chemotherapy
Drugs used to treat cancer can make saliva thicker, causing dry mouth.
Nerve damage
Injury to the head or neck can damage the nerves that tell salivary glands to make saliva.
