This test involves evaluating the UVA Protection Factor (UVAPF), which expresses a sunscreen product's level of protection across the entire UV spectrum, using a suitable substrate on which the product has been spread and measured using a spectrophotometric method.

(ref. HeUVA)

To take into account the photostability of your products, we recommend adding a UV exposure phase to your development tests. The sample is then exposed to UV radiation in a solar simulator at a specific dose before the sun protection is measured.

Taking photostability into account in your screening tests is a very important aspect, as all tests to official standards (ISO, FDA, etc.) include a UV exposure phase.

(réf. UVEXPO)

ISO/DIS 23698 (currently in progress at ISO level) proposes a hybrid approach combining in vitro and in vivo tests to assess the UV protection of sunscreens, in particular their UVA Protection Factor (UPF).
It uses diffuse reflectance spectroscopy (DRS) to measure UVA absorbance (320-400 nm) on the skin.
To obtain a complete UV absorbance spectrum, the in vitro absorbance values are adjusted according to the data obtained via DRS, enabling the in vitro UVB absorbance to be mathematically linked to the UVA portion measured by DRS.

*Available from WENEOS from January 2025.

ISO method 24443 specifies an in vitro procedure for characterizing the UVA protection of sunscreen products in a reproducible way. In order to determine the relevant UVA protection parameters, the method is strictly followed to provide a UV spectral absorbance curve from which a number of calculations can be made, such as the UVA protection factor (UVAPF). This method is based on the use of in vivo SPF results to scale the UV absorbance curve.

(ref. HeUVA-ISO)

ISO 24442:2022 - Cosmetics - Sun protection test methods - In vivo determination of the UVA protection of a sunscreen product - is based on the reading of a persistent pigmentation response of the skin to ultraviolet (UV) radiation from a calibrated artificial source. UVAPF is a ratio calculated from the minimum dose required to induce a persistent pigmentation response (MPPDD) with and without the application of sunscreen to the skin of human test subjects. The current method provides for static determination only.

*In vivo tests are carried out by our partners.

The statistical comparison method makes it possible to compare two sun protection products in terms of ageing, batch, benchmark, etc. When checking the absorbance spectrum between a reference and a test product using an in vitro method, two important rules must be observed. First of all, compare the two products at the same time and under the same conditions, to limit measurement variability. Secondly, a three-step verification based on absorbance values, including comparison of curve shape, variability and intensity.

(ref. HeCOMP-1)

Published method : *In vitro comparison - A new accessible and reliable statistical method to compare the global UV protection properties of cosmetics - Lutz and S. Miksa, H&PC Sun Care, July/August 2013 | *Sunscreen products: Some practical applications for a new comparison test method to help Development and ensure Quality Controls - D. Lutz, S. Miksa and C. Guy, H&PC Today, November/December 2014