Photodermatoses

Photo Facts

• The UV radiation (UVR) emitted by the sun is arbitrarily subdivided based on wavelength into UVA (400–320 nm), UVB (320–290 nm), and UVC (290–200 nm).

• More than 95% of UVR that reaches the earth’s surface is UVA.

• UVA, but not UVB, can penetrate through glass windows.

• The penetration of UVR into the skin is wavelength-dependent ( Fig. 73.1 ).

  

• Principles and formulations of sunscreens are discussed in the Appendix .