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Dandruff in the 21st Century
By: Steve Herman
Posted: October 26, 2012, from the November 2012 issue of GCI Magazine.
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However, ZPT must be carefully formulated in a shampoo and effectively deposited on the hair during use in order to be effective. And because ZPT is not soluble in shampoo base, it must be suspended, meaning a clear shampoo is not a possibility. ZPT particles come in different shapes and sizes, and only a proper particle can be uniformly deposited on the scalp. So the correct particle specification and an effective delivery system is a necessity for product performance. Once there, the ZPT controls the Malassezia yeast by interfering with transport through the cell wall.
Research pointing to new treatments for dandruff includes a paper by Holm3 studying the effects of antimicrobial peptides and cell-penetrating peptides on Malasezzia sympodialis, the most common yeast in individuals with atopic eczema. Several cell-penetrating peptides were shown to be nontoxic to mammalian cells while possessing growth inhibitory activity on the yeast.
Perhaps the most fascinating recent paper, very illuminating from a mechanistic prospective, is by Reeder4 and a large group of mostly P&G co-authors. They started by examining the activity of ZPT against a model yeast, Saccharomyces cerevisiae, because the model yeast is easier to work with than Malassezia globosa. However, they did extend the work to globosa, where they found ZPT to mediate growth inhibition through an increase in copper in the scalp fungus. The summary of the paper puts it succinctly in rigorously scientific prose: “A model is presented in which pyrithione acts as a copper ionophore, enabling copper to enter cells and distribute across intracellular membranes. This is the first report of a metal ligand complex that inhibits fungal growth by increasing the cellular level of a different metal.”
Chasing Better Results
To put this all more simply: Yeast living in the scalp use sebum as food. Part of the breakdown products of sebum is oleic acid, which irritates the skin. Cell turnover increases, flakes build up into clumps and they form visible dandruff. ZPT-containing shampoos interfere with the yeast cell by penetrating its walls and upsetting its internal ionic balance, leading to the death of the yeast and curing (at least temporarily) the dandruff condition.
This is pretty demanding science, but it is not often that a commonly used consumer product like an antidandruff shampoo can lead so deeply into the frontiers of research. And when a company like P&G publishes so much of its findings, it is an even more special opportunity to see the depth of the beauty industry’s commitment to understanding its products—and through that understanding making them better.
- TL Dawson Jr, Malassezia globosa and restricta: Breakthrough Understanding of the Etiology and Treatment of Dandruff and Seborrheic Dermatitis through Whole-Genome Analysis, J of Invest Dermatol Symp Proc, 12, 15–19 (2007)
- RB In and TL Dawson, The Role of Sebaceous Gland Activity and Scalp Microfloral Metabolism in the Etiology of Seborrheic Dermatitis and Dandruff, J Invest Dermatol Symp Proc, 10, 194–197 (2005)
- T Holm, et al, Cell-penetrating peptides as antifungals towards Malassezia Sympodialis, Lett Appl Microbiol, 54, 39–44 (2011)
- NL Reeder, et al, Zinc Pyrithione Inhibits Yeast Growth through Copper Influx and Inactivation of Iron-Sulfur Proteins, Antimicrob Agents and Chemother, 55:12, 5753–5760 (2011)
Steve Herman is president of Diffusion LLC, a consulting company specializing in regulatory issues, intellectual property, and technology development and transfer. He is a principal in PJS Partners, offering formulation, marketing and technology solutions for the personal care and fragrance industry. He is the New York Society of Cosmetic Chemists' 2013 Chapter Chairman and an adjunct professor in the Fairleigh Dickinson University Masters in Cosmetic Science program. He is also a Fellow in the Society of Cosmetic Chemists.