Using keratinocytes comes along with a lot of improvement and few disadvantages. First, we want to introduce the source of keratinocytes. There are different types of human hair, vellus, and terminal hair. Beside these two types of hair, there is the so-called Lanugo hair which usually appears only on the body of a fetus or newborn baby [64]. The change from vellus to terminal hair is androgen dependent. Thus, men exhibit more visible terminal hair than women. Starting with the puberty, due to the hormone modulation, terminal hair begins to replace the vellus hair. The crucial difference between these two types of hair is that terminal hair is more pigmented and thicker and it is connected to sebaceous glands [65]. For the establishing of keratinocyte cultures from hair follicles both, fine vellus as well as thick terminal hair can be used as the starting material.
