Dry mouth (xerostomia) occurs when the salivary glands are unable to work due to illness, certain drugs, or cancer treatments. This can make it difficult to eat, swallow, taste and talk. In some cases, such as radiation therapy, dry mouth can cause serious complications, which is why it is important to see a dentist immediately before starting any form of cancer treatment. Drinking plenty of water, avoiding candies, tobacco, alcohol, and caffeine are some ways to deal with dry mouth. Your dentist can also prescribe medication for severe dry mouth.