A shedding of hair is considered physiologically normal when hair loss is limited to around one hundred hairs per day. During an individual’s life hair grows, falls out and regrows around twenty times. Each cycle, especially for females, may last up to six years and if hair loss is found within this time frame, it is considered absolutely physiological.

Psychogenic alopecia is a type of hair loss related to stress. Though not yet scientifically explained, this connection is well-known in the experience of those working with the problem. In addition to stress, other causes are personality disorders, states of anxiety and depression, all of which are conditions of acute or chronic stress.

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.

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.