Q: Hi, I love your site and refer to it often. I was hoping you could answer my question. Last March I lost a lot of hair to
iron deficiency which hasnít grown back yet. Now I am having an autumn shed (which is normal for me) but because of my previous hair loss my hair is looking a lot thinner.
My question is: Once a hair is shed (under normal circumstances) how long is it before it is replaced and comes through the scalp?
A: Under normal circumstances, each hair follicle goes through three phases in the growth cycle of the hair. The anagen phase is the
phase in which the follicle grows new hair. This growth usually comes at approximately one-half inch per month. For the average
person, 90 percent of the hair follicles are in the anagen stage at any given time, and this stage lasts an average of 3-5 years, but can last as long as ten years in some individuals.
The catagen phase is a short stage that follows the anagen phase in which the growth of the hair in
the follicle is halted. The hair detaches and the root end shrinks. This usually takes one to two weeks, and then the hair follicle
enters a resting phase. In a normal situation, 1% of the hair is in the catagen phase at any given time.
The telogen phase is the resting phase of the hair. The hair that stopped growing in the catagen
phase may be shed during this stage, or it may remain in place until the next anagen phase, when new hair growth pushes it out of the
scalp. Usually about 10 percent of the hair is in the telogen phase at a given time, and this stage lasts from three to six months. As
soon as the telogen phase ends, the follicle resumes its anagen phase.
In your particular case, your doctor will be the one who can better tell you how long you may need to wait to see some return of your hair.