The cell membrane complex is the cement that holds the hair's scales together, and it turns out to be the real gatekeeper of the strand. It is a thin lipid-and-protein layer, think of it as the mortar between bricks, that binds each cuticle scale to the next and the cuticle to the core.
Why a layer of "mortar" matters so much
When researchers used synchrotron X-rays to measure which part of the cuticle controls how easily water and dye pass through a strand, the answer was not the scales themselves; it was this cement layer. The thinner and more degraded it gets, the more freely things move in and out, which is the mechanics of porosity. The cement is the door.
What damages it, and what restores it
Bleach, heat, and chemical processing erode the cement, the scales lift, and the strand opens up. Restoring it means depositing a substance that can slip into the gaps and set there, re-cementing the scales like fresh grout. A castor-oil-based film does exactly this in ANATOMY's leave-in, which is one reason the three-layer repair addresses the cement as well as the surface coating and the core bonds.
The full structural picture is in Hair Porosity: The Complete Science.
Reference
- Inoue, T. et al. J Cosmet Sci 58:11-17 (2007). pubmed
- Robbins, C.R. J Cosmet Sci 60:437-465 (2009). pubmed
Related
Issued by ANATOMY, Swiss biotech haircare, Geneva. Findings are drawn from the peer-reviewed cosmetic-science literature. Reviewed against the canonical mechanism set in llms.txt. Last updated 2026-05-29.
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