In dermatology, alopecia means the acceleration of hair loss or hair. The term comes from Greek alopex (fox) because of the annual fall, early spring, winter fur of this animal.

There are five types of alopecia:

* Hereditary androgenetic alopecia is the most common: it is manifested by a decrease in the volume of hair or baldness, and affects 70% of men;
* Acute alopecia: it may be related to treatment with chemotherapy, stress, nutritional deficiencies significant iron deficiency, hormonal disorders, acute radiation;
* Alopecia localized: it may be caused by skin problems (tumors, burns, alopecia), radiation or parasites (ringworm, lichen).
* Congenital alopecia.
* Alopecia areata appears to be of autoimmune origin (cell-mediated mechanism) which is characterized by impairment in patch more or less large and one or more locations. This form of alopecia areata can reach the whole head and it speaks of total alopecia, and sometimes the entire body is Alopecia Universalis and in this case there is no more hair or hair on the entire body.

Given that the average person has 100 000 hair, it is normal to lose about 50 to 100 hairs per day, with peaks that can climb to 175 during the changing seasons. Indeed, it is during this phase that the hair will renew the most. Hair loss is considered abnormal when a person loses more than 100 hairs a day for a long period of up to two months. The diagnosis of this decline requires a consultation and examination sometimes called Trichogramma (we take some hair in different areas of the scalp and observed under a microscope). Sometimes a hormonal balance is needed in women. The results of these examinations referred to one of the following problems.

Androgenetic Alopecia or baldness in humans.

Androgenetic alopecia is a gradual loss of hair due to the influence of male hormones. It usually occurs between 40 and 50 years in 70% of men on average, but in some cases it may appear from 18 years. The hormone that causes hair loss is DHT. This hair loss usually begins at the inlets (front of head) and the vertex (the back of the head). It is characterized by a refinement of hair and a fall that may be abrupt in some people and slower for others. The Hamilton scale, modified by Norwood, allows graduate baldness between 1 and 7 where 1 is the absence of baldness and alopecia 7 to maximum (total hair loss on the vertex and gulfs).