How does hair loss work?

The hair grows from the root or follicle, a narrow pocket under the skin. It goes through four phases: anagen, catagen, telogen, and exogen. The anagen is the growing stage that lasts for 2 to 7 years. The catagen is the transitional phase that lasts for 10 days, the hair shaft shrinks, and the dermal papilla starts to detach from the follicle. Telogen is known as the resting stage that lasts for 3 months, and 10% to 15% hair is in this stage. Exogen is also a part of the telogen phase where the old hair falls out, and new hair continues to grow. 50 to 150 hair can shed daily, but it is considered to be normal hair loss.