Event: 1599

Key Event Title


Inflamatory events in light-exposed tissues

Short name


Inflammatory events

Biological Context


Level of Biological Organization

Organ term


Key Event Components


Process Object Action

Key Event Overview

AOPs Including This Key Event


AOP Name Role of event in AOP
ROS-mediated chemical phototoxicity AdverseOutcome



Taxonomic Applicability


Term Scientific Term Evidence Link
human Homo sapiens High NCBI

Life Stages


Life stage Evidence
All life stages High

Sex Applicability


Term Evidence
Mixed High

Key Event Description


Photoirritation is frequently characterized as exaggerated sunburn sometimes mediated by oxidative stress in the cell membrane, and hyperpigmentation and desquamation may occur as a residual effect of a phototoxic reaction. Theoretically, if a high concentration of a phototoxic drug accumulates in the skin and the appropriate wavelength of light is present, any individual will develop a phototoxic reaction. In particular, peroxidation of membrane lipid could be induced by some photosensitizers under photo-irradiation, and this photochemical reaction certainly correlates with damage produced in the cell membrane, leading to the skin photoirritation (Castell et al. , 1994, Onoue et al. , 2009).

How It Is Measured or Detected


Inflammatory events induced by photoreactive chemicals can be detected in vivo phototoxicity testing and photopatch test in clinical (Epstein, 1964, ICH, 2014, Onoue et al., 2009). 

Domain of Applicability


Chemicals: This AO applies to a wide range of chemicals.  Phototoxic chemicals are recognized to have following characteristics: (i) absorption of light within the range of natural sunlight (290-700 nm); (ii) generation of a reactive species following absorption of UV-visible light; (iii) distribution to light-exposed tissues (e.g., skin and eye) in ICH S10 guideline for photosafety assessment (ICH, 2014).

Sex: This AO applies to both males and females. 

Life stages: The relevant life stages for this AO are all life stages after born.

Taxonomic: This AO mainly applies to human.

Evidence for Perturbation by Stressor

Regulatory Significance of the Adverse Outcome


Inflammatory events in light-exposed tissues are considered to be the endpoint of ROS-mediated chemical phototoxicity, especially photoirritant reactions (ICH, 2014, Onoue et al., 2009). 



Castell JV, Gomez-Lechon MJ, Grassa C, Martinez LA, Miranda MA, Tarrega P. Photodynamic lipid peroxidation by the photosensitizing nonsteroidal antiinflammatory drugs suprofen and tiaprofenic acid. Photochem Photobiol. 1994;59:35-9.

Epstein S. The Photopatch Test; Its Technique, Manifestations, and Significance. Ann Allergy. 1964;22:1-11.

ICH. ICH Guideline S10 Guidance on Photosafety Evaluation of Pharmaceuticals.: International Council on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use; 2014.

Onoue S, Seto Y, Gandy G, Yamada S. Drug-induced phototoxicity; an early in vitro identification of phototoxic potential of new drug entities in drug discovery and development. Current drug safety. 2009;4:123-36.