Key Structural Components of Skin: Keratin, Collagen, Elastin, Hyaluronic Acid, and Sebum

Keratin

Type: Fibrous structural protein (α-keratin in epidermis/hair/nails).
Function: Forms the stratum corneum—waterproof, protective barrier against mechanical, chemical, and microbial insults. Provides tensile strength.

Collagen

Type: Triple-helix fibrous protein (Type I & III dominant in dermis).
Function: Provides tensile strength, structural scaffolding, and firmness. Declines ~1%/year after age 20; UV accelerates degradation.

Elastin

Type: Highly cross-linked elastic protein.
Function: Allows skin to stretch and recoil (elasticity). Works with collagen for resilience. Degraded by UV (elastosis) and aging.

Hyaluronic Acid (HA)

Type: Glycosaminoglycan (GAG), non-sulfated.
Function: Binds 1000× its weight in water → hydration, volume, turgor. Facilitates cell migration, wound healing. Molecular weight determines penetration.

Sebum

Type: Lipid mixture (triglycerides, wax esters, squalene, cholesterol).
Source: Sebaceous glands (attached to hair follicles).
Function: Lubricates skin/hair, antimicrobial (free fatty acids, low pH), antioxidant (vitamin E), transports fat-soluble antioxidants.

Clinical Note

These "non-living" components are continuously synthesized and degraded by living cells (keratinocytes, fibroblasts, sebocytes). Balance determines skin health, aging, and disease.