The SPF value reflects the level of sunburn protection offered by sun care products and is connected to the protection against DNA damage. The current gold standard for SPF testing, ISO 24444:2019, involves testing on human volunteers. This is the only accepted method, but the procedure is invasive, complex, time consuming, and costly.
The cosmetics industry has been working in the past years to find suitable alternative methods. However, analysing and characterising new methods for public use demands sophisticated analytical tools. Also, comparing alternative SPF data against the gold standard requires a solid set of in vivo SPF data and thus represents a significant experimental effort that should not be repeated for each alternative method.
This is how, in 2018, the idea for the ALT-SPF initiative was born
Bringing together a critical mass of SPF test users to evaluate new methods
The ALT-SPF consortium seeks to evaluate, characterise and compare alternative SPF methods that are less invasive, more precise, and more cost-effective to the current gold standard, ISO 24444:2019, and to publish the results obtained in peer-reviewed journal(s).
The ALT-SPF consortium selected a set of 32 sunscreen samples that represent a reasonably large spectrum of product types and SPF levels found in the market and for which the alternative methods are applicable.
ISO 24444:2019 testing
SPF samples will be tested according to the SPF in vivo method ISO 24444:2019. Each sample will be tested by four labs in two independent set-ups.
Alternative method testing
SPF samples will be tested using different alternative methods. Each sample is tested by four labs in two independent set-ups for each alternative method being evaluated:
- Double plate method (ISO Draft 23675)
- HDRS method (ISO Draft 23698)
- Fused method
- In silico method
- LED-HDRS method
For each alternative method, test results will be obtained on the basis of the selected samples and compared to the test results obtained from the same samples tested with the gold standard, ISO 24444:2019.
Method characterisation report
The alternative methods may show random variation together with some bias in relation to the gold standard. It is essential to characterise the methods by applying a statistical model that will make it possible to decompose total error in its different components.
The results of the study will be published in a peer-reviewed journal.
The work carried out by ALT-SPF could be used by norming or standardisation bodies as a basis to harmonise and develop standard methods for sun protection.