It’s the eternal dilemma: those with straight hair would like to have them curly or at least wavy… and vice versa!
What makes hair straight or curly? The basic answer is quite obvious: they depend on genetics.Concretely, however, the shape of the hair is determined by the hair follicles, sack-shaped structures found on the skin and within which the hair and body hair are born. The section and the shape of the follicle, therefore, determine the structure of the hair, directing their training and growth: this is how we can have a straight, curly or wavy hair.
There are three types of follicles based on their section and shape:
Round section follicles (lissothricic) and straight shape determine straight hair (the Oriental type)
Flat section follicles (ulotrichous) and helical shape give rise to curly hair (the Negroid type)
Oval section follicles (cymotrichous) determine the wavy hair (the Caucasian type); here the shape of the follicles is variable and therefore explains the great variety of curly, smooth or wavy hair in Caucasians.