Why do some people have fine and curly hair?

Whether your hair is straight or curly depends on how the papillae – the hair roots – perform. If the follicles have a regular pattern or growth is uneven, you hair will be curly. Two factors decide the texture of your hair: the diameter of the follicles and the amount of hard casing on each individual hair. If the follicles are small in diameter, the hair will be fine and sometimes difficult to control – in the wind, for example.

Each hair consists of a shell, known as the cuticle, and a softer, fibrous inner substance, the cortex. Fine hair has 40 percent cuticle and 60 percent cortex; coarse hair has only 10 percent cuticle and 90 percent cortex. Whether your hair is coarse or fine makes no difference to whether it will turn grey or leave you bald later in life.