Radical production by infrared A irradiation in human tissue

Skin Pharmacol Physiol. 2010;23(1):40-6. doi: 10.1159/000257262. Epub 2010 Jan 14.


The influence of the ultraviolet (UV) irradiation of the sun on the formation of free radicals in human skin is well investigated. Up to now, only small amounts of data are available stating that infrared (IR) irradiation can produce free radicals in the skin. In the present study, the formation of free radicals in human skin, subsequent to IRA irradiation (600-1,500 nm), has been demonstrated by means of two different methods. Firstly, the radical formation was detected indirectly by the degradation of the cutaneous carotenoid antioxidants beta-carotene and lycopene, which was investigated in vivo by resonance Raman spectroscopic measurements. Secondly, the direct observation of produced radicals subsequent to IRA irradiation of the skin was performed in vitro by electron paramagnetic resonance spectroscopy. Taking into account the results of the present study and previous UV light studies, it can be expected that also solar irradiation in the visible spectral range will produce free radicals in the human skin. Therefore, the current sun protection strategies should be reconsidered. Furthermore, it was shown in the present study that the side effect in the form of radical formation could be significantly reduced by increasing the protection system of the human organism in form of the antioxidant network.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Antioxidants / metabolism
  • Antioxidants / radiation effects
  • Carotenoids / metabolism
  • Carotenoids / radiation effects
  • Electron Spin Resonance Spectroscopy
  • Female
  • Free Radicals / radiation effects*
  • Humans
  • Infrared Rays / adverse effects*
  • Lycopene
  • Male
  • Skin / metabolism
  • Skin / radiation effects*
  • Swine
  • beta Carotene / metabolism
  • beta Carotene / radiation effects


  • Antioxidants
  • Free Radicals
  • beta Carotene
  • Carotenoids
  • Lycopene