To put it plainly, a hair cuticle is the outermost layer of a hair strand. It’s what protects your hair from damage and imparts shine.
Although a single strand of hair is made up of three layers, the only one that’s visible to the human eye is the cuticle. It’s like a protective shield that makes sure the other more fragile layers are intact. Whether your hair is smooth and shiny or frizzy and dull is an indicator of the health of your cuticles.
Another indicator of cuticle health is your hair porosity, which the New York Society of Cosmetic Chemists defines as how much your hair absorbs or retains water, hair products, and hair treatments. There are three types of hair porosity.
Low porosity
Low porosity hair tends to resist the absorption of water and chemical treatments. It also typically takes a lot of time to dry, easily experiences product buildup rather than absorption, and tends to be less responsive to heat or chemical treatments. Hair types with low porosity: Curly, coily, or chemically straightened hair with a coarse structure.
Medium porosity
Medium porosity hair absorbs and retains water fairly well. It easily accepts chemical treatments with predictable results. Hair types with medium porosity: This is the ideal hair porosity. If you’re lucky enough to have it, your cuticles are in great shape.
High porosity
High porosity hair is highly processed hair that has been compromised by exposure to chemicals or physical stress. It’s quick to wet and dry, tends to experience frizz and breakage easily, and has an overall dry feel. Hair types with high porosity: Frizzy, dry, or dull hair that may be damaged by excessive dyeing or chemical treatments.
