Treatment is according to cause. Causes of dry mouth include: side effect of certain medications. Dry mouth is a common side effect of many prescription and nonprescription drugs, including drugs used to treat depression, anxiety, pain, allergies, and colds (antihistamines and decongestants), obesity, acne, epilepsy, hypertension (diuretics), diarrhea, nausea, psychotic disorders, urinary incontinence, asthma (certain bronchodilators), and parkinson's disease. Dry mouth can also be a side effect of muscle relaxants and sedatives. Side effect of certain diseases and infections. Dry mouth can be a side effect of medical conditions, including sjgren's syndrome, hiv/aids, alzheimer's disease, diabetes, anemia, cystic fibrosis, rheumatoid arthritis, hypertension, parkinson's disease, stroke, and mumps. Side effect of certain medical treatments. Damage to the salivary glands, the glands that make saliva, can reduce the amount of saliva produced. For example, the damage could stem from radiation to the head and neck, and chemotherapy treatments, for cancer. Nerve damage. Dry mouth can be a result of nerve damage to the head and neck area from an injury or surgery. Dehydration. Conditions that lead to dehydration, such as fever, excessive sweating, vomiting, diarrhea, blood loss, and burns can cause dry mouth. Surgical removal of the salivary glands. Lifestyle. Smoking or chewing tobacco can affect how much saliva you make and aggravate dry mouth. Breathing with your mouth open a lot can also contribute to the problem.