Hair Growth Cycles (and why they are important for Hair Removal)
Understanding how hair grows helps us to understand how to remove it effectively. Hair grows in cycles and each individual hair can be in any of the following phases of the growth cycle
- anagen (or growing) phase
- catagen (involuting or regressing) phase
- telogen (resting or quiescent) phase
- exogen (shedding or exit) phase
During the anagen phase hair is actively growing and receives nourishment via the hair follicle. This growth slows during the catagen phase, stopping altogether during the telogen phase. During the telogen phase the hair is no longer supplied with nourishment and becomes detached from the papilla. The hair then falls out (exogen phase).
The whole cycle can take 3 or 4 years on the head and that is why you can grow very long hair there. The growth cycle for other parts of the body is much shorter so that the length of potential hair growth is limited (for which we can be truly thankful)!
Up to about 90% of head hair follicles are usually in the anagen phase at any one time with about 10% in telogen and 1 - 2% in catagen but the cycle time varies for different parts of the body. In some parts of the body, the active growing phase is proportionately shorter so that only half of some areas (including those requiring treatment to remove excess hair) may be in the anagen phase at any one time.
The amount of time in each phase is also determined by genetics, hormones and it is different for men and women.
Some methods of removing hair (such as electrolysis) need hair to be in the anagen phase to have a permanent effect as this is when the hair is more susceptible to the "injury" caused by the treatment which has the aim of stopping the unwanted hair from growing and renewing itself. This means a single area of excess hair cannot be treated in one go with permanent results. There will always be a large proportion of hairs which were at the wrong stage in the cycle and were not successfully treated. Although the therapist knows that only hair in the anagen phase can be permanently removed he or she has to treat all the hairs as it is not possible to determine the stage of hair growth during the hair removing process.
This is one of the reasons why removing excess hair by some methods can be so costly and time-consuming. Hair has to be treated over and over again until the therapist is able to catch all the hairs at the right point in the growth cycle.
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