If you’re confused about how to approach skin corrosion testing for your substance, whether for hazard identification and labelling for regulatory compliance or within the new product development process, our new guide is here to help.
The guide is a concise and practical overview of the various in vitro tests that have full approval for this important human health endpoint, and contains the latest regulatory guidance. Download your copy using the link below.XCellR8 Guide to skin corrosion testing (39 downloads)
IATA on Skin Irritation and Corrosion
The guide starts by looking at the OECD’s Guidance Document 203: Integrated Approach to Testing and Assessment (IATA) on Skin Irritation and Corrosion, which was published in 2014 and articulates a clear approach, including a flow diagram summarising the 3 essential parts of the assessment: review of data, weight of evidence analysis and additional testing.
It isn’t always necessary to conduct additional testing, but when it is, it’s important to consider whether you expect your substance to be corrosive / irritant or not, and to adopt the “top-down” or “bottom-up” approach respectively.
How to choose the right skin corrosion test for your needs
Three skin corrosion tests have full regulatory approval:
- Reconstructed human epidermis (OECD TG 431)
- Membrane barrier (OECD TG 435) known as Corrositex®
- Transcutaneous electrical resistance (OECD TG 430)
TG 430 isn’t a true in vitro method as it requires animal sacrifice to provide the rat skin, and in some countries may be considered an in vivo animal experiment due to the shaving, washing and treating steps for 4-6 days prior to sacrifice. It also doesn’t provide any option to sub-classify corrosives and it has the lowest predictive potential of the 3 tests. As an animal-free lab, we don’t provide this test at XCellR8.
Our recommended approach focuses on choosing either or both TG 431 and TG 435 depending on sub-classification needs and the nature of the test substance. The reconstructed skin model method is suitable for a wide range of substances and formulations and is able to distinguish between corrosive sub-categories 1A vs 1B/C.
The Corrositex® method can sub-categorise 1A, 1B and 1C but is only applicable to substances of very high or low pH (typically excluding pH 4.5-8). If you’re not sure which is the most appropriate strategy for you, we’re always happy to discuss this.
Animal-free methods should be the default
It’s important to note the regulatory expectation for these in vitro tests to be fully utilised for the assessment of skin corrosion.
Recently-updated statistics on animal testing, released by the EU*, state “There is a concern with the uses of animals in areas where alternative methods have reached regulatory acceptance (for example in areas of skin irritation/ corrosion, serious eye damage/eye irritation and pyrogenicity testing), which requires further attention by the authorities authorising projects for these use purposes.”
In the UK, more than 110 rabbits are still used in Draize tests annually. We’re currently seeking clarification from the Home Office on why these tests are still being authorised and what is the rationale behind these decisions. Ultimately, we need to ensure adoption of animal-free methods is accompanied by the retirement of old tests, to prevent their ongoing and unnecessary use and drive uptake of the more human-relevant models that have full OECD approval.
The XCellR8 Guide to Skin Corrosion testing is available to download as a pdf here, or it was first presented as a webinar for the Chemical Hazards Communication Society (CHCS) in January 2020. You can listen to the recording plus Q&A session here.
* 2019 report on the statistics on the use of animals for scientific purposes in the Member States of the European Union in 2015-2017