Recent advances in urocanic acid photochemistry, photobiology and photoimmunology

Photochem Photobiol Sci. 2008 Jun;7(6):655-67. doi: 10.1039/b717398a. Epub 2008 Mar 13.


Urocanic acid (UCA), produced in the upper layers of mammalian skin, is a major absorber of ultraviolet radiation (UVR). Originally thought to be a 'natural sunscreen', studies conducted a quarter of a century ago proposed that UCA may be a chromophore for the immunosuppression that follows exposure to UVR. With its intriguing photochemistry, its role in immunosuppression and skin cancer development, and skin barrier function, UCA continues to be the subject of intense research effort. This review summarises the photochemical, photobiological and photoimmunological findings regarding UCA, published since 1998.

Publication types

  • Review

MeSH terms

  • Animals
  • Carcinogens / pharmacology
  • Humans
  • Immune Tolerance / drug effects
  • Immune Tolerance / radiation effects*
  • Photobiology
  • Photochemistry
  • Urocanic Acid / chemistry*
  • Urocanic Acid / immunology
  • Urocanic Acid / metabolism
  • Urocanic Acid / radiation effects*


  • Carcinogens
  • Urocanic Acid