There are many causes of dry mouth. Dry mouth most commonly occurs as a side effect of medications that cause decreased saliva production, including high blood pressure medications, antihistamines, antidepressants, diuretics, nonsteroidal anti-inflammatories, narcotics, and many others.
Liquid diet: The Liquid diet is the restriction of solid food intake, and replacement of solid food with liquids. In hospitals, liquid diets are prescribed by doctors for a number of reasons for patients who are unable to consume solid foods. Liquid diets may be prescribed following surgery or as a preparation for certain medical procedures.
A clear liquid diet is often suggested when a person is suffering from a form of gastritis or gastroenteritis. Severe vomiting and diarrhea leads to a loss of fluids in the body and causes dehydration; this is where the clear liquids can help to replace fluids, but is easy on the stomach.