Inability to cry. Blurred vision. Photophobia (light intolerance). Dryness of other mucosae, e.g., nasal, laryngeal, and/or genital. Burning sensation. Itching or grittiness. Dysphonia (voice changes). There may also be other systemic signs and symptoms if there is an underlying cause such as Sjögren's syndrome, for example, joint pain due to associated rheumatoid arthritis. Cause The differential of hyposalivation significantly overlaps with that of xerostomia. A reduction in saliva production to about 50% of the normal unstimulated level will usually result in the sensation of dry mouth. Altered saliva composition may also be responsible for xerostomia. Physiologic Salivary flow rate is decreased during sleep, which may lead to a transient sensation of dry mouth upon waking. This disappears with eating or drinking or with oral hygiene. When associated with halitosis, this is sometimes termed "morning breath". Dry mouth is also a common sensation during periods of anxiety, probably owing to enhanced sympathetic drive. During periods of stress, our body responds in a ‘fight or flight’ state that will interfere with the saliva flow in the mouth. Dehydration is known to cause hyposalivation, the result of the body trying to conserve fluid. Physiologic age-related changes in salivary gland tissues may lead to a modest reduction in salivary output and partially explain the increased prevalence of xerostomia in older people. However, polypharmacy is thought to be the major cause in this group, with no significant decreases in salivary flow rate being likely to occur through aging alone. Drug induced Aside from physiologic causes of xerostomia, iatrogenic effects of medications are the most common cause. A medication which is known to cause xerostomia may be termed xerogenic. Over 400 medications are associated with xerostomia. Although drug induced xerostomia is commonly reversible, the conditions for which these medications are prescribed are frequently chronic. The likelihood of xerostomia increases in relation to the total number of medications taken, whether the individual medications are xerogenic or not. The sensation of dryness usually starts shortly after starting the offending medication or after increasing the dose. Anticholinergic, sympathomimetic, or diuretic drugs are usually responsible. Sjögren's syndrome Xerostomia may be caused by autoimmune conditions which damage saliva-producing cells. Sjögren's syndrome is one such disease, and it is associated with symptoms including fatigue, myalgia and arthralgia. The disease is characterised by inflammatory changes in the moisture-producing glands throughout the body, leading to reduced secretions from glands that produce saliva, tears and