Unexpected distribution of surface hydration level of the lip

BACKGROUND: The functional properties of human lips depend on their hydration level. Limited data are, however, available. OBJECTIVE: To investigate water distribution through the lower lip surface. METHODS: Images from the surface of the lip were recorded using a new capacitance imaging technique. Capacitance and conductance measurements were also carried out in various points of lower lip and on adjacent skin. RESULTS: Data clearly show that the closest part of the mucosa of the lip is less hydrated than the external part. These unexpected findings could be related to the presence of a premucosa area whose structure is clearly different from that of vermilion zone.