Hydrolyzed Keratin: What It Is and Why It's Used

Origin

Keratin is the fibrous structural protein that makes up hair, nails, and the outer layers of skin. Commercial keratin for cosmetic use is extracted from animal sources — most commonly wool, feathers, or hooves — through a hydrolysis process that breaks the protein into smaller polypeptide fragments. The use of hydrolysed proteins in hair care dates from the mid-20th century, when the connection between protein loss and hair damage was established.

Why It's Used

The fragments produced by hydrolysis are small enough to penetrate the hair shaft, where they can temporarily bond with damaged areas of the hair's internal structure. The conditioning effect is genuine but temporary — washing removes the deposited fragments. Claims about keratin 'rebuilding' the hair's own structure beyond this temporary deposition are not substantiated by the evidence to the standard of this series.

Elsewhere

Keratin proteins and derivatives are used in wound healing research and tissue engineering. Hydrolysed proteins from various sources (collagen, silk, soy) are used similarly in cosmetics; the specific source affects marketing positioning more than functional differentiation.

What the Framework Sees

Question 3, and arguably the strongest case of it in this entire series.

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