The phase in the hair cycle marked by rapid and active hair growth
The hair cycle is the cyclical phases of growth of hair. It is comprised of the following stages: anagen, catagen, telogen, and exogen. Each hair fiber goes through these stages. However, the hair fibers are at different stages of the hair cycle that occur simultaneously.
Anagen is the first phase in the hair cycle. It is referred to as the growth phase as it is the phase wherein the hair is actively growing. The human hair could grow to about 1 cm every 28 days. The hair on the scalp typically grows to about .3 to .4 mm per day (about 6 inches per year).1 Depending on the genes controlling this phase, the hair strand would remain in this stage and grow to a certain length. For instance, the typical length range of scalp hair is 100 to 1000 mm, the eyebrow is about 5 to 10 mm, and the pubic hair is about 10 to 60 mm.2 The next phases after anagen are catagen, telogen, and exogen. The next anagen occurs when the new hair grows in the hair follicle.
1Hair Loss: The Science of Hair. (2011). Retrieved from ://www.webmd.com/skin-problems-and-treatments/hair-loss/science-hair#2.
2 Peytavi, U. (2008). Hair growth and disorders. Berlin: Springer. p.10