The daily saliva production in a normal human being is three pints. Saliva is a substance that lubricates the mouth and aids in speech. It protects the teeth against decay by helping to wash away food debris, by limiting the growth of bacteria, and by neutralising acid. Saliva makes swallowing easier and the enzymes contained in saliva aid with digestion. Mouth dryness or xerostomia results from inadequate saliva production by salivary glands located in the mouth or oral cavity.A mouth is one of the body parts that offer multiple entries of micro-bacteria into the body. The food we eat leaves some residues behind and the saliva is there to ensure adequate cleansing of the mouth all the time.Germs such as bacteria and fungi have a symbiotic relationship with our oral environment, and saliva offers protection against their outgrowth. This is because if they overgrow, they will migrate down to other parts of the body to cause life threatening diseases.Reasons for the cause of dry mouth are usually different from those of chapped lips, though they have one in common–dehydration.Symptoms of dry mouth include red tongue with burning sensation on the tongue and in the mouth, persistent thirst due to urgent need for hydration, dental problems, frequent yeast infections and sometimes pain during swallowing.  Bad breath is also a major symptom of mouth dryness. The patient with this symptom will have other problems like difficulty to speak and trouble to chew. They tend to have a poor taste to food materials. Other symptoms include thick, stringy saliva and potential sores or split creases at the corners of the mouth.   Causes of dry mouth can be age, medications, lifestyle especially on the kind of drinks, diseases or sickness and cancer therapy.Dry mouth can be a result of aging. The relationship between age and mouth dryness is that as we get older, we produce less saliva. This condition is complicated by a degeneration of the thirst receptors in the brain. In such circumstances, your brain does not tell you the thirsty you have or suffering. And as a consequence of your age, the person is producing less saliva anyway, and together the two factors results in dry mouth.When dry mouth occurrence is gradual, then age is behind the elicitation of the problem. But if it occurs suddenly, then medical experts should intervene to trace the underlying cause.There as some medications when taken without adequate liquid or fluid will likely cause mouth dryness. For the dryness to disappear, this means a person will have to change medications, but all too often the condition cannot be traced to one cause and must be controlled rather than cured.In some cases of dry mouth syndrome especially in older people, some types of medications tend to bring about mouth dryness. Drugs for depression and anxiety cause dry mouth as do antihistamines, blood pressure prescriptions, muscle relaxants, and medications for urinary incontinence. If the patient suddenly begins to experience dry mouth after receiving a new prescription, he or she should ask health experts about the medication you are taking and see if an alternate medication is available without the side effect of dry mouth.Medical conditions or sickness that cause mouth dryness include Alzheimer’s disease, endocrine disorders such as diabetes, stroke, anxiety, depression, and various autoimmune diseases among others.Stress induced mouth dryness is common in younger people and will usually resolve itself with rest and increased intake of fluids.The lifestyle causes of mouth dryness include use of tobacco products, cigarettes, cigars, and pipes or chewing tobacco and snuff aggravate dry mouth and given their link to cancer, should be avoided any way. Drinks with high sugar concentrations like caffeine, sodas, and sugar tea should be checked. Cancer patients on chemotherapy will have particularly difficult time with dry mouth. The chemotherapy drugs effect the composition of saliva and the degree of its production. Radiation treatments for cancer may actually damage the salivary glands and prevent them from functioning normally.Dr Joseph Kamugisha is a resident oncologist in Jerusalem, Israel