In the ideal world you'd empirically test all significant aspects of your formulas, to design better ones and to give people an accurate idea of what your product does.
Is there a way to do this on a budget for moisturizers? I know AMAlabs (not sure what's happening with the FBI probe) could do 2% SLS challenge testing and do tewameter readings for around $500/subject with two test points. You'd probably want to do more than one subject too to reach statistical significance.
Are there and more affordable empirical methods to get at least an estimation of moisturization effect? How do you validate the efficacy of your moisturizer formulas?