Xerostomia is a state where the mouth lacks saliva, giving an uncomfortable feeling of dryness. If not treated, xerostomia can lead to problems with eating, talking and initiate halitosis(bad breath). It can also aggravate periodontal disease and trigger an increase of the number of cavities.

Dry mouth has many causes, including bad habits, some prescribed drugs or even existing diseases such as these:

• Sjögren's syndrome is an autoimmune disorder in which immune cells attack and destroy salivary glands that produce saliva.
• One of the signs of iron deficiency anaemia is dry mouth.
• One of the signs cystic fibrosis is also dry mouth.
• Some patients with rheumatoid arthritis develop Sjögren's syndrome, which leads to dry mouth and dry eyes.
• One of the side effects of having HIV (AIDS) is dry mouth.
• Alzheimer's disease causes frequent dehydration, therefore dry mouth is a problem in Alzheimer's patients, particularly in the later stages.
• Dry mouth may be the symptoms of undetected or badly treated diabetes.
• One of the side effects of high blood pressure medication is dry mouth.
• Some Parkinson's disease's medication also causes dry mouth.
• Cancer treatments, which include chemotherapy and radiotherapy, can cause dry mouth as well.
• A person who has suffered from stroke is very likely to have dry mouth.
• One of the symptoms of mumps is dry mouth.