Scientific Area:
Hair and Scalp

A hair follicle is a formation of epidermal origin, anchored in the dermis and consisting of a hair and its sheath. The formation of hair follicles occurs early. They begin to appear as early as the second month of gestation. These follicles will continue to form for the entire duration of the pregnancy. At birth, the baby will indeed have the entire supply of follicles with which it was genetically equipped and from this moment on, no others will form.

Some parameters and characteristics should be taken into consideration when assessing hair types and morphologies: shape, density and appearance. The appearance of hair, in the form of lanugo, occurs during the fourth month of pregnancy.

The life cycle of hair and its subsequent growth occur at a speed of 1-1.5 cm per month. Hair is a living element that follows a follicle cycle with an average duration of 2-6 years. In humans, unlike other mammals that are subject to a periodic change, this cyclic evolution is not synchronous (therefore each hair is independent from the others).

The sebaceous glands are glands that secrete sebum, an oily, acidic substance with a pH of 3.5. They are connected laterally to the hair follicle. Sebaceous glands are found with a density of approximately 100/cm2 throughout all areas of the skin. In the human body, they are located across the entire surface of the skin, except for the palms of the hands and the soles of the feet. Sebaceous glands are also found in the external auditory meatus (ear canal) and on the eyelids, where they are long and flat. Here they are called tarsal or Meibomian glands.

The hair on our bodies has a particular structure and is divided into thin and thick hair. Thin hair, also called lanugo or vellus, is located on all skin surfaces except for the palms of the hands and the soles of the feet. Thick hair, also called terminal hair, is dark and located only in some areas such as the scalp, the armpits, the pubic area, the beard area in the case of men, etc…

The scalp is an ultra-specialized area of the skin, where hair is anchored. Like other hair, also the hair on the scalp originates from a hair follicle, called a bulb.