Properties of Hair – Part 3

In the third installment of the properties of hair, lipid or fat content of the hair shaft will be our subject. The lipid content of hair is approximately 1-9% .

The lipids found in hair are tightly bound to the proteins via various bonds, and as such, are referred to as Integral Hair Lipids.  They confer resistance  to the hair shaft, protecting it from the environment by forming a lipid envelope. Most of the lipids are found in the the hair cuticle and inner root sheath. Major constituents are fatty acids, phytosphingosine, and ceramide in decreasing order. Minor constituents are cholesterol, cholesterol sulfate and cholesterol oleate. Interestingly the lipid components differ from the skin to hair follicle to the hair shaft.

Table showing lipid constituents in hair and skin compartments

The major fatty acid, representing 40% of the total fatty acids, is identified as 18-methyleicosanoic acid. The next abundant are palmitic acid and stearic acid. Alkaline treatments (hair colorings, bleaching, perms) or sunlight can lead to a loss of 18-MEA and causes the defatting of hair. As such, the hair becomes dry and brittle and loses its elasticity and luster.

They all serve to decrease the friction between the hair strands. Their role in hair are slowly being delineated. Their presence may indicate something more important with respect to the functioning of the body. Ceramide production has been found to decrease with age. Also, it has been found that errors in lipid metabolism could result in abnormal skin and hair diseases.  As more and more research is done, we shall see the exact role they play in hair.