This test involves evaluating the Sun Protection Factor (SPF), 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. HeSPF)

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 Sun Protection Factor (SPF).
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/DIS 23675 (currently in progress at ISO level) involves assessing the sun protection factor (SPF), which expresses a sunscreen product's level of sun protection across the entire UV spectrum, using a multi-substrate approach (molded and sandblasted plates) on which the product has been spread and measured using a spectrophotometric method. This method allows better correlation with In Vivo results. To take account of possible photoinstability, the product was pre-irradiated before measurement.

(ref. HeSPF-ISO)

ISO 24444 - Cosmetics - Sun protection test methods - In vivo determination of sun protection factor (SPF) - is based on the reading of a skin erythemal response to ultraviolet (UV) radiation from a calibrated artificial source. SPF is a ratio calculated on the basis of the dose required to induce a minimal erythemal response (notion of Minimum Erythemal Dose - MED) with or without application of a sunscreen product to the skin of human test subjects. The current method provides for static determination only.

*In vivo tests are carried out by our partners.

FDA 2011 21 CFR Parts 201 and 310 - Labeling and Effective Testing; Sunscreen Drug Products for Over-the-Counter Human Use - Food and Drug Administration (U.S.) - is based on the reading of a skin erythemal response to ultraviolet (UV) radiation from a calibrated artificial source. SPF is a ratio calculated on the basis of the dose required to induce a minimal erythemal response (notion of Minimum Erythemal Dose - MED) with or without application of a sunscreen product to the skin of human test subjects. The current method involves a static and water resistance determination.

*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