Skin sensitisation, adverse outcome pathways and alternatives

Area of Science:

• Toxicology
• Dermatology
• Computational Chemistry

Background:

• The last two decades have seen significant evolution in skin sensitization testing methodologies.
• Traditional guinea-pig assays are being replaced by refined methods like the Local Lymph Node Assay (LLNA) and increasingly by in vitro and in silico approaches.
• Risk assessment strategies have also evolved from 'black box' methods to quantitative approaches, now facing a period of uncertainty.

Purpose of the Study:

• To review the fundamental changes in skin sensitization testing over the past two decades.
• To discuss the evolution of risk assessment data usage for human safety assurance.
• To highlight the importance of mechanistic understanding and human health protection in skin sensitization assessment.

Main Methods:

• Review of historical and current methodologies in skin sensitization testing.
• Analysis of the progression from animal-based assays to in vitro and in silico models.
• Discussion of the shift in risk assessment paradigms from qualitative to quantitative and the current challenges.

Main Results:

• The field has transitioned from traditional animal testing (guinea-pig assays) to more refined methods (LLNA) and is moving towards in vitro and in silico approaches.
• The use of testing data for human safety assurance has evolved, presenting new challenges and uncertainties.
• A focus on intrinsic chemical properties, mechanistic foundations of tests, and human health protection is emphasized.

Conclusions:

• Skin sensitization testing is rapidly advancing with a move towards non-animal methods.
• The interpretation and application of test data for human safety require careful consideration of mechanistic insights.
• The ultimate goal of all skin sensitization research must remain the protection of human health.