Once a product or material has been shown to be non-irritating in a single application patch test, the next step is to confirm that the product will not be irritating with exposures of longer duration. The 3-Patch Application Test (3-PAT) is commonly used for this purpose. The exposure conditions of the 3-PAT are highly exaggerated over any exposures that would be encountered in real-life circumstances. Therefore, it is considered a very rigorous test of the potential to cause irritation.
In the 3-PAT, a dilution of the test material is applied to the upper arm using a small patch, and left in place for 24 hours. After that time, it is removed and replaced with a fresh patch. This is repeated for a total of 3 applications (72 hours of patching).
In our tests with Lenor, we chose to use only those volunteer panellists who reported that they had "sensitive skin". We pre-screened the panellists using a "sting" test: a commonly used method to identify individuals with sensitive skin for testing cosmetics and other topically-applied products. We confirmed sensitive skin in 111 volunteer panellists. These sensitive skin volunteer panellists were patched with a 0.2% solution of two different Lenor formulations.Result:
The 3-PAT confirmed that Lenor was mild to the skin, even for individuals with sensitive skin, under conditions where the exposure was highly exaggerated over those that would be encountered in real-life circumstances.