Dear Valerie: Do you prefer in vitro or in vivo testing when looking at claims testing from ingredient suppliers? —Vivo Vitro

Dear Vivo:

After careful consideration, I have to say both, yet neither. In vitro testing is useful for screening materials to understand their full potential. However, they don’t exactly translate to real-life formulation outcomes because—for skin—penetration through the outermost layers may be presumably a requirement, and hair tress testing is not necessarily equivalent to what a consumer experiences. I’ve had plenty of hair care products test well in on-head testing with trained evaluators, exceeding consumer testing expectations, yet did poorly through in vitro testing.

In vivo testing can overcome this hurdle, but the study must be well designed. Often studies have an unsuitable control or placebo, or an n that is too small to be significant. One time I saw a manufacturer study where n equaled 1. Can’t make it up!

I am most weary about consumer perception studies from ingredient manufacturers because the manufacturer may not necessarily report “consumer response” metrics that are not flattering to the ingredient.  In my work, anything manufacturer-supplied is used as an indication to how an ingredient could perform and I always recommend brands to set aside a small budget to conduct their own clinical and consumer perception testing.

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Valerie George

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Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com