Abnormal dryness of the mouth resulting from decreased secretion of saliva. It is characterized by a smooth, red mucosa, difficulty with speech and eating, reduced taste sensation, a greater incidence of periodontal disease, an increased potential for cervical and smooth surface caries, and a tendency towards fungal infections. It also has a detrimental effect on the retention of complete dentures. Xerostomia may be a sign of underlying disease such as Sjögren's syndrome, diabetes, and connective tissue diseases, or it may result as a side-effect from medication such as chemotherapy and some antidepressants, alcohol, radiation therapy, or the taking of drugs such as cannabis and methamphetamine. Tumours or trauma to the salivary glands may also reduce salivary secretion. Treatment is usually directed at the underlying condition but where this is impossible it is focused on relieving the symptoms by the use of mouthwashes, saliva substitutes, reservoir bite guards, sugar-free chewing gum, and extensive oral hygiene instruction and monitoring.