Figure 1. Different follicle shapes determine the shape of the hair


  • Whether it is straight, curly or wavy, hair shape differs from individual to individual. But what’s the biology behind?
  • Being a biologically dead material, its shape varies from different factors, mostly genetics.

Hair has several biological functions. A strand of hair is composed of two main components: the shaft and the hair follicle. The hair follicle is a complex structure, placed deep inside your skin. In simple words, you can say that a follicle is the organ responsible for hair production. Hair follicle directly impacts the shape and texture of the hair that it produces. The shape of the follicle, in turn, is affected by the genes that you inherit from your parents. The shape of each hair follicle is thought to be determined during embryonic development (Yella Hewings-Martin, Ph.D., 2017). The way that the cells divide and produce certain proteins in curly hair is asymmetrical and correlates with the bends in the curved follicle. This results in a hair fibre that has an elliptical shape, which allows it to curl. Genetic factors appear to play a major role in determining hair texture and thickness in people of different ethnic backgrounds. So far, the main driver that has been identified is a gene that produces a protein called trichohyalin (TCHH), which strengthens the growing hair. The TCHH gene contains distinct variants called small nuclear polymorphisms, which are associated with different hair shapes in people across the globe (Yella Hewings-Martin, Ph.D., 2017). For example, in individuals of East Asian decent, variations in the gene for the receptor EDAR are associated with straight, coarse hair. The nature of follicles directly impacts the curvature of hair strands. If the follicles are symmetrical, hair grows to be straight, whereas if the follicles are asymmetrical, they produce oval-shaped hair that tends to curl as it grows (Scienceabc, 2017).

Hormones, certain medications, and chemicals such as hair relaxers can alter the characteristics of a person’s hair (U.S National Library of Medicine). Hair texture and thickness can also change with age.


COPYRIGHT: This article is property of We Speak Science, a nonprofit institution co-founded by Dr. Detina Zalli (Harvard University) and Dr. Argita Zalli (Imperial College London). The article is written by Elona Xhemaili (State University of Tetovo, Master of Pharmaceutical Sciences, Macedonia)