[Cause 1: The shape of the hair root is congenitally different]

Since people's hair roots are congenitally shaped differently, the hair that grows out will inevitably be curly or straight. As shown in the photo below, you can see that curly hair (left) has curved roots, while straight hair (right) has straight hair roots. There are also people with a mixture of curly and straight hair (middle).

[Cause 2: Acquired changes due to aging, etc.]

Many people experience changes in their hair quality as they age. The data below presents representative examples from 230 Japanese women in each age group. As you get older (A→B→C), the percentage of curly hair tends to increase.

Congenital differences in the shape of hair roots and acquired changes in hair due to aging, etc., both have a common cause: an imbalance in the shape of the hair and the cortex cells that make up the hair.
The figure below shows a cross-section of straight and curly wool. You can see that straight hair has a circular cross-section, while curly hair has an oval cross-section. There is also a difference in that the two types of cortex cells (green and red) are concentric in straight hair and skewed in curly hair.

[If the shape of the hair root is congenitally different]

It has been said that congenital curly hair is difficult to treat, but research on curly hair has revealed the following, which could be a target for treatment.

Research has revealed that after treatment for alopecia areata, there are cases in which the hair quality in the area of ​​hair loss changed from curly to straight. (Figure below) Possible causes include changes in the differentiation process of hair root stem cells and the effects of cytokines and hormones.

Mouse experiments have also suggested that dysfunction of growth factors and transcription factors, as well as genetic mutations, may be the cause of curly hair. It has been demonstrated that it is possible to improve curly hair by administering active ingredients derived from stem cells using stem cell culture supernatant liquid or PRP treatment.

[In the case of acquired changes due to aging, etc.]

In addition to aging, lifestyle factors, stress, lack of sleep, and damage caused by coloring, perms, etc. are also factors, so improving the fundamentals will lead to treatment.

It is thought that the hair roots become deformed due to poor blood circulation and sagging of the scalp, which causes curls and frizz.

As a specific measure...