Both sets of complaints, mouth dryness and a burning sensation of the oral mucosa, can have a variety of causes. Local and regional as well as systemic causes can be responsible for burning mouth syndrome. Diseases of the oral mucosa can have genetic, inflammatory, or neoplastic origins. Autoimmune diseases and allergies as well as different afflictions relating to internal medicine can be accompanied by a burning sensation in the oral mucosa. Neurological and psychiatric illnesses must be clarified during interdisciplinary diagnostics in order to identify idiopathic forms. The causes of mouth dryness are similarly complex. In addition to inadequate fluid intake, particularly in elderly patients, drug side effects or systemic diseases are frequently also responsible. Treatment is directed at the underlying disease; in ambiguous cases, symptomatic therapy can provide relief for medical complaints.