Validated in vitro methods are available for skin irritation testing without animals for the hazard assessment of most agents within the EU. However, the total elimination of animals for skin irritation testing depends upon the acceptance of the validated in vitro methods by the regulatory authorities (Grindon, et al., 2007). The recent acceptance of the draft OECD TG for in vitro skin irritation testing will promote the wider use and acceptance of the in vitro methods. The assessment of reversibility and the dose response data needed for risk assessment for skin irritation cannot be totally replaced with the current validated in vitro methods (ECVAM, 2005). For these latter testing applications, additional refinement of the in vitro methods and their validation for the intended purposes needs to be completed.
In vitro methods for skin corrosion are sufficient for both hazard and risk assessment purposes in the EU and for many regulatory purposes in the US. Acceptance of in vitro data for skin corrosion depends upon the regulatory authority, and a case can usually be made for its acceptance.
Scientists at the Fund for the Replacement of Animals in Medical Experiments (FRAME) have identified the need for better in silico models for skin irritation/corrosion and for improving the predictive capability of existing in vitro skin models (Grindon, et al., 2007). Some specific recommendations they made for in vitro skin models were:
- wider use of the IL-1α endpoint
- research to identify additional toxicity endpoints
- improved in vitro skin models, including co-culture models
- in vitro protocols for repeat dose testing and recovery
A more recent assessment of the IL-1α endpoint indicates it may not be necessary for improving the accuracy of the in vitro assays validated for hazard identification of chemicals (Kandárová, et al., 2009; Alépée, et al., 2010).
For more on The Way Forward, read the following invited commentary on skin irritation/corrosion toxicity testing:
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