What Is a Hair Cuticle?

Every hair strand is made up of three layers, the cuticle, cortex and the medulla.

• What is the hair cuticle?  The hair cuticle is the outermost surface layer of the hair strand. It’s comprised of over-lapping layers of dead cells that form a protective barrier, in the same way that roofing shingles form a protective cover and barrier on a house. The cuticle layer plays a crucial role in maintaining the health and appearance of the hair.

• What is the hair cortex?  Underneath hair’s outer cuticle layer you’ll find the middle layer, known as the cortex. The cortex makes up the bulk of your hair mass. It’s the cortex that gives hair strength and defines whether your hair is fine, normal or thick. The cortex is also home to the pigments (colors) that determine your hair shade, whether natural or artificial coloring from chemical dye molecules. The cortex consists of long keratin (protein) filaments, which are linked together by disulphide and hydrogen bonds. The integrity and elasticity of these bonds is what determines how strong, resilient and supple your hair is. 

• What is the hair medulla? The medulla is hair’s innermost section, typically found only in very thick hair types. It’s made up of soft, thin transparent cells and air spaces.

What does a healthy cuticle look like?

A healthy cuticle is smooth and flat, so it creates a unified, reflective surface (this is what gives your hair the quality of shine!). When the cuticle layer is flat and tight, it acts as a barrier to stop critical inner moisture from leaching out AND to stop excess moisture (humidity!) from entering the strand and making it puffy. A closed, smooth cuticle is the key to keeping your hair properly hydrated, promoting strength and flexibility, and preventing frizz.

What does a damaged cuticle look like?

A damaged cuticle layer looks rough, ragged and uneven. When the cuticle layer is raised, individual hair strands can’t fall in smooth, sleek, flat alignment. The overall effect of a raised cuticle layer is dry, dehydrated hair that looks dull, puffy and frizzy. 

Can you open/close a hair cuticle?

The cuticle can be opened by heat styling, chemical treatments (perms, hair color, bleach, hair straighteners) aggressive brushing or styling (tight braids or weaves, use of tight elastics) or environmental stressors like UV rays which can lead to dry, frizzy, and unmanageable hair. Even showering with very hot, steamy water can force open hair’s outer cuticle layer. 

An open-cuticle is the first sign of damage....and could lead to more serious hair problems like dehydration and breakage. Once the cuticle layer is lifted by any of the factors mentioned above, it never closes permanently. But there are several types of hair products and new cuticle-smoothing treatments and appliances that can dramatically smooth, seal and hold the cuticle closed and flat for an extended time.

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