On average, 100 hairs are physiologically shed on a daily basis throughout the human scalp, at random. The hair cycle is also subject to chronological influences. For example, during the autumn months, daily hair shedding may double, while there is diminished shedding in the spring. Both the duration of hair growth and the daily growth rate are greater in summer than winter.
In humans, follicular activity has a mosaic pattern (dysynchronous), with neighbouring follicles being at different stages of the hair growth cycle. At any given moment in time, roughly 90% of the terminal hair is in the growing phase and the other 10% is resting. Consequently, we can summarize that the hair cycle consists of three phases: