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Hair Loss Info

Hair Loss Info

Hair Growth Stages

Hair strands do not grow continuously, but in stages. Normal hair grows about 6 inches per year. There are three stages of growth : anagen, catagen, and telogen. In the anagen stage, the hair is in its active growth stage. The cells in the hair root are dividing rapidly and new hair is formed which pushes hair that is no longer growing up and out of the hair follicle. During this phase, the hair grows about 2.5 inches every 28 days. Scalp hair remains in this growth phase from 2 to 6 years. In the catagen phase, the hair transitions from growing to the end of the growth stage in which it will eventually be pushed out by the hair in the anagen stage. This lasts for 2-3 weeks and about 3% of all hairs are in this stage. In the telogen phase, the hair is in a resting phase. 6-8% of all hair is in this phase. This phase lasts for about 100 days for scalp hair. About 25-100 telogen hairs are shed daily.

Hair Loss Causes

The most common reason for hair loss is genetics, and is referred to as androgenic alopecia (AGA) – commonly called male or female baldness. There are other non-AGA alopecia, most notably telogen effluvium, alopecia areata, scarring alopecia, ringworm, and hair loss due to cosmetic over-processing.


Hair loss characterized as effluvium is loss attributed to interference with one of the stages of hair growth.
Telogen effluvium (TE) appears as a thinning of the hair. It occurs because the number of hair follicles producing hair significantly drops. This increases follicles in the resting stage and the result is shedding of the hair. The condition is reversible. TE can be brought upon by changes in hormones, physical trauma, certain prescription drugs or crash diets. Long-term illness can also bring about TE.

Anagen Effluvium

Anagen effluvium (AE) is a thinning of the hair like TE but can spread more quickly and can lead to total hair loss. AE is most frequently seen in people taking cytostatic drugs for cancer. Drugs of this type inhibit rapid cell proliferation and this inhibits hair fiber proliferation as well. The growth stage is thus inhibited, which leads to excessive hair shedding. After a person has finished taking these drugs, the hair follicle will start to proliferate again, and slowly he/she will start to see hair growth.

Alopecia Areata

Alopecia Areata (AA) is the third most common type of hair loss. AA is caused by autoimmune disease such as rheumatoid arthritis. The individual’s immune system attacks hair follicles and inhibits hair follicles from growing. Just why or how AA develops is not clear. The hair follicle is not completely destroyed so it can recover and resume normal growth stages. There are some prescription drug treatments for this as well.

Scarring alopecia

Scarring alopecia refers to a number of hair loss disorders that are associated with diseases that affect the hair follicle and/or larger organs in the body. Scarring alopecia results in hair follicle destruction and permanent hair loss.


Ringworm is a fungal infection that can occur on the scalp and cause patches of hair loss. Ringworm is contagious but can be medically treated. If treated, there is no permanent hair follicle destruction.


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