The hair cycle
Our hair goes through cyclically 3 growth phases, which last three to five years each. Of course, not all hairs go through this cycle at the same time, but each hair runs this cycle in itself time-delayed to the other hairs.
In the first and longest phase, the anagenic phase, the hair lengthens daily for 3–5 years.
In the subsequent so-called katagen phase, the hair follicle shrinks and detaches from the blood supply in the scalp and transitions into a kind of resting state. This phase lasts only a few weeks.
During the transition to the final phase of hair growth, the telogen phase,
the hair follicle triggers the hair shaft and the hair falls out.
This is a natural process and not a cause for concern, as the loss of 100–200 hairs a day is considered normal. A healthy follicle usually regenerates and reconnects to the blood connection of the scalp to form a new hair shaft.
This three-phase cycle repeats itself again and again, how often this happens is genetically predetermined, just like our hair length. However, if the natural cycle is shortened by nutrient deficiency or the influence of the hormone dihydrotestosterone (DHT), it can lead to increased to complete hair loss and so we lose our hair well before our genetically predetermined time.