dysfunction, xerostomia is one of the most prevalent and persistent oral symptoms associated with COVID-19. Despite a close association with COVID-19, xerostomia, dry mouth and hyposalivation tend to be overlooked in COVID-19 patients and survivors, unlike ageusia, dysgeusia and hypogeusia. Diagnostic approach A diagnosis of hyposalivation is based predominantly on the clinical signs and symptoms. The Challacombe scale maybe used to classify the extent of dryness. The rate of the salivary flow in an individual's mouth can also be measured. There is little correlation between symptoms and objective tests of salivary flow, such as sialometry. This test is simple and noninvasive, and involves measurement of all the saliva a patient can produce during a certain time, achieved by dribbling into a container. Sialometery can yield measures of stimulated salivary flow or unstimulated salivary flow. Stimulated salivary flow rate is calculated using a stimulant such as 10% citric acid dropped onto the tongue, and collection of all the saliva that flows from one of the parotid papillae over five or ten minutes. Unstimulated whole saliva flow rate more closely correlates with symptoms of xerostomia than stimulated salivary flow rate. Sialography involves introduction of radio-opaque dye such as iodine into the duct of a salivary gland. It may show blockage of a duct due to a calculus. Salivary scintiscanning using technetium is rarely used. Other medical imaging that may be involved in the investigation include chest x-ray (to exclude sarcoidosis), ultrasonography and magnetic resonance imaging (to exclude Sjögren's syndrome or neoplasia). A minor salivary gland biopsy, usually taken from the lip, may be carried out if there is a suspicion of organic disease of the salivary glands. Blood tests and urinalysis may be involved to exclude a number of possible causes. To investigate xerophthalmia, the Schirmer test of lacrimal flow may be indicated. Slit-lamp examination may also be carried out. Treatment The successful treatment of xerostomia is difficult to achieve and often unsatisfactory. This involves finding any correctable cause and removing it if possible, but in many cases it is not possible to correct the xerostomia itself, and treatment is symptomatic, and also focuses on preventing tooth decay through improving oral hygiene. Where the symptom is caused by hyposalivation secondary to underlying chronic disease, xerostomia can be considered permanent or even progressive. The management of salivary gland dysfunction may involve the use of saliva substitutes and/or saliva stimulants: Saliva substitutes – These