In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan.


The term alopecia means hair loss regardless of the cause. It is not exclusive to the scalp; it can be anywhere on the body. Everyone is born with hundreds of thousands of hair on the head. The hair cycle consists of three phases: the growth phase, which is called anagen, the resting phase, which is called catagen, and the shedding phase, which is the telogen phase. Ninety percent of hair are in the growth phase (anagen) and the rest, which corresponds to ten percent in the resting and shedding phases. When hair is falling out, this is the telogen phase, and the hair is going to recycle, and it starts growing again in the (growth) anagen phase. Alopecia can be subdivided into two main categories: scarring and non-scarring.

The most common type is non-scarring or androgenetic alopecia. The majority of men start to lose hair in the twenties, while women begin to lose their hair in their forties or fifties. As an individual grows older, they will lose hair. The difference between male hair loss and female hair loss is the pattern. Men generally lose hair in the front and the temporal region, while women tend to lose hair from the central area of the scalp. Also, female hair loss will not end up with complete baldness, whereas male hair loss can end up with complete baldness. Males tend to retain hair at the posterior area of the scalp because this hair is resistant to the androgenic hormone.

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