Between two identical experimenters, each having the same harmless test material, the one participating as a willing guinea pig is much more likely to realize subtle effects compared to the one that does not.
A carefully selected variety of Aloe is my only current gardening effort. The fresh gel of the living plant has benefits to the skin not possessed by lesser forms. Commercial formulations are (at the least) thousands of years less advanced than the natural plant.
This guy is the solution to all our product testing problems!