Now that I think about it, an easy test could've comparing the skin of people who do/don't regularly swim in chlorinated pools. I'd think that the chlorine would pretty much nuke any surface microbiome. So the comparison would be fairly straightforward. Hardly definite, with all the possible confounding factors and all, but certainly an easy way to test for plausibility.
I wouldn't trust any study in concert with a cosmetics company to be impartial/sensible science. They're aiming for a result that increases revenue for their products (or leads to products that can generate revenue for them), and this would drive how the study is constructed.
L’Oreal wants to make money by selling products that improve a person’s appearance. Having a better understanding of the biology behind aging skin could aid that endeavor, so I wouldn’t write this research off as a matter of course.
I doubt they would support a study that possibly conclude to use less of their products, or they might test a number of hypotheses and then only pursue a published study on whatever makes cosmetic products appear better. It's sensible to write off any study that has such a clear conflict of interest in doing actual science.
Yeah I think at some point we'll discover that we bathe far too frequently. Our skin did not evolve under conditions of daily washing with soap or detergent.
