Our hairs grow and regrow in a repeated cycles and each cycle can be divided into three phases.
- Anagen Phase
- Catagen Phase
- Telogen Phase
The anagen phase is the growth phase and approximately 85% of our hairs on the scalp are in this phase at any time. The duration of this phase is 2-6 years. In a year, hair grows approximately 10 cm. The anagen phase is followed by the catagen phase which is of 3-6 weeks duration. During this phase the hair follicle shrinks to about 1/6 of the normal length in anagen. The catagen phase is followed by the telogen phase. During this phase hair does not grow but remains attached to the follicle. At the end of the telogen phase, the hair enters into a new anagen phase again where the dermal papilla and the base of follicle join together to form new hair regrowth. Hair growth is a continuous process following the above cycle.
In healthy individuals, the hair fiber grows at a rate of approximately 0.35 mm/day on the scalp. Also in a normal scalp, the total number of follicles in the growth phase is constant. It is the duration of the anagen phase that determines the maximum hair length and also the number of hairs that will complete the telogen phase and will fall off.
When there is an imbalance in the normal cyclical process of hair regrowth or when the follicle is damaged, hair loss or alopecia occurs.
Factors affecting normal hair regrowth
A variety of factors can affect the normal cyclical process of hair regrowth. Some of the common factors are medication, radiation, chemotherapy, exposure to chemicals, improper hair styling, hormonal and nutritional factors, thyroid disease, generalized or local skin disease, and stress.
One or more of these factors can cause serious hair fiber damage like loose anagen syndrome or irreversible hair loss like scarring alopecia. Infectious diseases like tinea capitis can also be a cause of hair loss.
Temporary disruption in the cyclical process of hair regrowth
Hair regrowth can also be affected by temporary disruption of the cyclical process. Some of the factors that involve temporary disruption of the hair regrowth cycle are after a baby's birth, surgery, getting anesthesia, etc. Strong cancer treatments often lead to anagen effluvium, a major cause of hair loss for those undergoing chemotherapy.
Adequate information about the hair loss causes, will help you in hair loss treatment. Remain informed about the exact mechanism of hair growth and how it cycles. Also, have a brief overview on the factors and diseases that can affect the normal hair regrowth system. |
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