1. Selective absorption of light and heat decomposition:
Reason: The hair shaft and hair papilla absorb a lot of light. Light energy is converted into heat. Instantly heat up, and burst broken hair papilla. And then hair dry and shedding and decaying.
2, According to the hair growth cycle (growth period, prosperous period.

3, Normally, there will be no hair within 3 – 5 years. Even hair regrowth again, the hair will very fine fluff, which does not affect the appearance.