Standard Article


Target Organ and Tissue Toxicity

  1. J. Frank Nash PhD

Published Online: 15 DEC 2009

DOI: 10.1002/9780470744307.gat175

General, Applied and Systems Toxicology

General, Applied and Systems Toxicology

How to Cite

Nash, J. F. 2009. Phototoxicology. General, Applied and Systems Toxicology. .

Author Information

  1. The Procter & Gamble Company, Central Product Safety, Cincinnati, Ohio, USA

Publication History

  1. Published Online: 15 DEC 2009


Phototoxicology is the study of adverse events resulting from the interaction between light and a test material. Measurement of the target chromophore absorption profile is the first step in a phototoxicological assessment. Determination of acute photoirritation potential is achieved using the in vitro 3T3 neutral red uptake phototoxicity assay. The photoirritation or photoallergenicity potential of a test material may be evaluated using in vivo animal testing. Human evaluations of photoirritation or photoallergy potential are available to confirm the absence of such effects. Long-term photo co-carcinogenicity testing has been evaluated using the SKH1 albino hairless mouse model. This is often preceded or replaced by photogenotoxicity testing; for example, in vitro photo-Ames, photoclastogenicity studies. For either photo co-carcinogenicity or photogenotoxicity testing, the outcome interpretation is often uncertain due to the absence of known human positive controls and the predictive validity of such studies. In the USA and Europe, there are regulatory guidelines for photosafety testing of pharmaceutical/cosmetic test materials. The multivariate nature of phototoxicology requires careful attention to the experimental conditions and photobiological considerations, for example light source and dosimetry. Any potential photohazard identified using in vitro or in vivo methods must be judged in the context of product use and light exposure.


  • absorption;
  • photoirritation;
  • photoallergy;
  • photogenotoxicity;
  • photo co-carcinogenicity