> ## Documentation Index > Fetch the complete documentation index at: https://eraorganics.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Keratin: the skin's structural protein > Keratin is a fibrous structural protein that makes up the tough outer layer of skin cells. It is a type of structural protein — the same broad family that… ## What is keratin? Keratin is a fibrous structural protein that makes up the tough outer layer of skin cells. It is a type of structural protein — the same broad family that gives hair and nails their strength — and in the skin it is what provides rigidity and resilience to the surface. Ingredient and biology writing uses a few interchangeable names for it: the general term is keratin protein, the skin-specific form is called cytokeratin, and the plain phrase skin keratin covers the version packed into surface cells. All three describe the same fibrous material. Keratin is defined by its structure, and that structure explains its toughness. It is built from long amino acid chains that coil and pair into keratin filaments, and those filaments are locked together by disulfide bonds — strong sulfur-to-sulfur links that resist water and mild chemicals. This cross-linking is why keratin is so durable: it is not easily dissolved, which is exactly what the outer skin needs from a protein meant to shield everything beneath it. ## Where keratin sits in the skin Keratin is part of the stratum corneum, the outermost layer, where it fills the flattened surface cells. It is also part of dead skin cells specifically — each corneocyte is essentially a keratin-filled shell. Those cells are produced by keratinocytes, the living cells lower in the epidermis that manufacture keratin as they mature and rise. As a keratinocyte reaches the surface it loses its nucleus and hardens into a keratin-packed corneocyte, a maturation described in a 2013 study of [cornification](https://pubmed.ncbi.nlm.nih.gov/23792051/), the terminal step in which keratin-filled corneocytes form the surface. Those same keratinized cells are then shed from the top, the desquamation documented in a 2000 paper on the [shedding of keratinized cells](https://pubmed.ncbi.nlm.nih.gov/10891569/). So keratin has two faces. Inside living skin it is a helpful, protective scaffold. But once it is locked into dead cells that overstay their welcome, that same toughness becomes a nuisance — a keratin buildup that makes the surface feel rough and look dull. The natural opposite of intact, cross-linked keratin is dissolved protein, a soluble peptide whose bonds have been broken so it no longer holds cells together. ## How exfoliation works on keratin Getting keratinized dead cells off the surface means loosening the protein that holds them there. That happens two ways. A physical scrub uses friction to lift the flakes that are already loose. An enzyme goes further and works on the keratin itself: [papain, a papaya-derived enzyme](/products/face-exfoliation-scrub/papain), cleaves the bonds of keratin in dead corneocytes so they release from the surface. It is the proteolytic enzyme in the [Face Exfoliation Scrub](/products/face-exfoliation-scrub). Papain acts on the protein of spent cells while living skin is shielded by natural protease inhibitors, which is what makes enzyme exfoliation feel gentler than aggressive scrubbing. This is why the scrub is described as dual-action. The micronized rounded walnut-shell powder buffs the loose [buildup of dead skin](/concepts/dead-skin-cells) mechanically, and the papaya enzyme helps break down keratin bonds in the stubborn flakes that friction alone would leave behind. Together they lift keratinized cells away and reveal smoother-looking skin, then aloe vera and manuka honey soothe the fresh surface. ## Frequently asked questions about keratin ### What is keratin in the skin? Keratin is a tough, fibrous structural protein that fills the cells of the outer skin layer. Built from coiled amino acid chains cross-linked by disulfide bonds, it gives the surface its strength and forms the hard shell of each dead corneocyte. ### Does exfoliating break down keratin? Enzyme exfoliation does work on keratin: papain, a papaya-derived enzyme, cleaves the protein bonds of keratin in dead surface cells so they lift away. Physical scrubbing does not dissolve keratin but buffs off the flakes it holds together. The scrub uses both. ### Is keratin the same as dead skin? Not quite. Keratin is the protein; dead skin cells are the corneocytes packed with that protein. When people talk about keratin buildup they usually mean an accumulation of keratin-filled dead cells on the surface, which gentle exfoliation helps lift away. ### Why does keratin make skin feel rough? Keratin is durable and cross-linked, so when keratin-filled dead cells pile up instead of shedding on schedule, the surface turns firm and uneven to the touch. Lifting that layer away with regular exfoliation helps the skin feel smoother again. ## Era Organics and keratin The Era Organics Face Exfoliation Scrub is a dual-action cosmetic scrub built to lift keratin-filled dead cells from the surface and reveal smoother-looking skin. It pairs micronized, rounded walnut-shell powder for physical buffing with papaya enzyme (papain) that loosens the keratin bonds of dead corneocytes, then soothes with aloe vera, manuka honey, and vitamin E. It is made for facial skin and body, best used 2 to 3 times a week rather than daily. Because it contains walnut, a tree nut, and manuka honey, patch test first and skip it if you have a tree-nut or bee-product allergy. It is a cosmetic for the look and feel of your skin — for a medical skin condition, see a clinician.