The hydro-lipid layer is composed of hydro (water) and lipids (fats) which form a thin emulsion that coats the hair and skin of mammals to keep both hydrated and in optimum condition. It is infused into the keratin of the hair’s cuticle as it’s formed in the follicle and the outer surface is continuously replenished via secretions from the sebaceous glands. This delicate barrier is comprised of essential fatty acids, ceramides, tryglicerides, cholesterol and water. Essential fatty acids comprise a greater proportion of the lipid layer and contribute to hair’s elasticity and aid ceramides in keeping the cuticle scales attached to the hair shaft.
The hydro-lipid layer provides two primary functions; hydration and protection. It’s present on the outside of the hair shaft forming a continuous film, and it’s also present within the cuticle layer. It is a permeable lining that allows for the uptake of water but it also is occlusive enough to slow the evaporation of moisture from the shaft. Lubrication is another function of this layer which prevents cuticles from lifting or snagging on other surrounding hair strands. When the hydro-lipid-layer is damaged or completely removed, the hair loses a vital source of consistent moisture, the rigid cuticle scales are left exposed to mechanical damage and other insults, and the vital cement that holds cuticles in place is compromised. Subsequent loss and damage of the cuticle layer leaves hair porous, rough, absent of gloss or elasticity and vulnerable to breakage.
The delicate hydro-lipid layer can be disturbed by a number of activities that many people consider to be part of their normal hair care routine. Shampoos that contain strong sulfates and a high pH are a prime culprit in the disturbance of the lipid coating. By their nature, sulfates function by rendering oil water miscible so that it can be removed from the hair and scalp. A shampoo that is intended to be mild, gentle or moisturizing will still operate according to this principle but will not strip the hair and scalp bare of all its essential fats. Without proper protection, chemical treatments like hair coloring or relaxers can damage or completely dissolve lipids from the hair shaft. Vital lipids can be removed from the surface of the cuticle layer as well as from in between the cuticle scales, weakening the natural cement that holds them fast to the hair shaft. The constant application of high heat to the hair is also a common cause of damage to the hair’s protective barrier.
The easiest way to maintain this vital portion of the hair is to minimize or eliminate hair styling practices that place it in jeopardy. If you routinely undertake actions that compromise the lipids in your hair, be certain to use quality moisturizing products that contain essential fatty acid-rich ingredients that restore and replenish the hydro-lipid layer’s integrity.
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