LEVEL C SUB ITA SKIN

During anagen, there is a marked reduction in the number of melanocytes in the hair follicles through autophagolysosomal degeneration leading to pigment loss. In gray hair, the pigmentary unit becomes fuzzy, the melanocytes become few and rounded, and lightly pigmented oligodendritic melanocytes become visible in the proximal hair bulb. The pigmentary unit is a pear-shaped black structure at the tip of dermal papilla in pigmented hair. Hair is actively pigmented in the anagen phase and is “turned off” during the catagen phase and absent during telogen.

LEVEL C SUB ITA SKIN

Each melanocyte is associated with five keratinocytes in the hair bulb forming a “hair follicle-melanin unit.” In contrast, each melanocyte in the skin is associated with 36 keratinocytes constituting an “epidermal-melanin unit.” Unlike in the skin where pigment production is continuous, melanogenesis in the hair is closely associated with stages of the hair cycle. There are various differences between pigmentation in the skin and that of hair. A study in 2012 showed a recessive mutation in tyrosinase-related protein 1 (TYRP1) in people with blonde hair This mutation is seen usually in individuals of Northern Europe with less sun exposure. A mutation in melanocortin-1 receptor (MC1R) gene causes auburn or red color of hair. As pH reduces, there is a progressive reduction in tyrosinase activity leading to increased pheomelanin and reddish or blonde hair. It has been hypothesized that the pH and cysteine level of melanosomes influences the phenotype of hair. The diversity of hair color arises mostly from the quantity and ratio of black-brown eumelanin and reddish-brown pheomelanin. Human hair follicles contain two types of melanin as follows: eumelanin and pheomelanin. The color of human hair is due to pigment melanin produced by melanocytes which are neural crest derivatives. Hair pigmentation is one of the most unique features in humans ranging from black, brown, and blonde to red. A large population-based study reported that 6%–23% of people have 50% gray hair by 50 years of age. The average age of the onset of graying in Caucasians is 34 ± 9.6 years, and in Blacks, it is 43.9 ± 10.3 years. Definition of PGH with respect to the Asian population is lacking. PGH is defined as graying of hair before the age of 20 years in Caucasians and before 30 years in Blacks. However, the age at which it occurs varies in different races. Graying of hair also called canities or achromotrichia occurs with normal aging. As graying of hair is perceived as a sign of old age, premature graying of hair (PGH) can bear an adverse effect on the self-esteem of the individual. Hair color and style can significantly alter the physical appearance of a person and thus alter his/her body image. Nevertheless, hair serves as a great esthetic tool and means of nonverbal communication. Unlike other animals, the function of hair in human beings is being debated. Haalthy hair is a sign of general well-being and youth.

Level c sub ita