Day 2 of the 13th International Sun Protection Conference provided a fascinating insight into the problems, advances and alternatives to established in vitro testing methodology. This was a major part of the day, with five presentations providing insights for improving accuracy, consistency and repeatability of SPF tests. Sun protection has been around for 20 years, but it is still very difficult to standardise tests and results.
In vivo testing has many problems, from questions about the morality of deliberately exposing people to sun damage to consistency and reproducibility. In addition, the time and expense involved can compromise results as companies are reluctant to carry out extensive tests due to the time and expense involved. Testing of cosmetics on animals is illegal in many jurisdictions and is fast becoming commercial suicide on ethical grounds.
This has meant a renewed focus on laboratory testing, either in vitro or in silico, where the comparative performance needs to be determined. Problems with in vitro include film consistency and distribution, irradiation spectrum differing from sunlight and the variability of results between laboratories. In silico measurements often under-estimate the SPF of high SPF products.