Non-invasive cosmetic efficacy testing in human volunteers: some general principles

The Sixth Amendment to the European Union's Cosmetics Directive 76/768/EEC requires "proof of the effect claimed for the cosmetic product, where justified by the nature of the effect or product". To avoid unnecessary claim support disputes, it may be helpful for there to be discussion in the literature to clarify what is generally considered to be sufficient proof of efficacy. Certainly most will wish to encourage efficacy study methodologies which simultaneously (a) ensure an adequate level of quality based on accepted principles of good scientific investigation; (b) are broad and flexible so that detailed procedure can be adapted to suit local needs and conditions; (c) are relevant to the needs of producers, regulatory authorities and consumers.

To progress these aims, it appears that the same basic set of considerations arises in all contexts. This is outlined under a series of key headings in the present paper, which may serve as a basis for further discussion.