The Challacombe scale is a widely used diagnostic medical tool designed to produce a clinical oral dryness score (CODS) which quantifies the extent of dryness of the mouth, with the aim of making a decision of whether to treat or not, and to monitor its progression or regression.

[4] Dry mouth (xerostomia) is frequently caused by medication and to a lesser extent, by anxiety or Sjögren's syndrome.

That is, if a person has a complaint of a dry mouth, the clinician can apply the Challacombe scale to determine its severity and whether treatment is required.

The scale also provides a common reference point, allowing progress or deterioration to be monitored.

[3][4] The score correlates with the rate of salivary flow and with the wetness of the mouth, indicated by the thickness of the mucosal film on the inside of the cheeks, on the palate and on the tongue.