A study of physical light screening agents

SUMMARY In those photodermatoses in which the action spectrum involves wavelengths outside the short ultraviolet (i.e. >320 nm) little protection can be obtained against long UV (>320 nm) by the application of chemical light screening agents. An action spectrum involving wavelengths >320 nm is a common occurrence and may necessitate the additional provision of protection from a physical light screening agent. Such a physical agent is titanium dioxide and in a study of its use in a variety of formulations using in vitro techniques it was shown to be effective throughout the wavelengths 400‐700 nm. It was also shown to have a satisfactory protective capacity in those photodermatoses in which the action spectrum involves wavelength peaks 365 nm (335–395 nm) and 400 nm (370–430 nm). It also has a reasonable cosmetic acceptability provided care is taken to incorporate in the formulations colouring agents which can be varied to suit the individual patient.