The Life Cycle of a Hair and Electrolysis / Laser Hair Removal

Why is it that you have to have multiple sessions of laser hair removal and electrolysis in order to get long lasting results?  The answer concerns the life cycle of a hair and how effective the various treatments are during each phase.

Hair Growth and The Genetic Factor

Hair growth is determined genetically and differs from person to person.  The rate also depends on age, metabolism and even the location of the hair on the body.  

For example, armpit hair has a much shorter lifecycle (around 4-5 months) than leg hair (around 12 months).​

Hair Growth by Body Part

A table called the "Richards-Merhag" table illustrates the growth rate for each area of the body.

Body Part



Cycle Duration


3 months

1-2 weeks

10 months


3 months

1-2 weeks

10 months


10 weeks

2-3 weeks

14 months

Upper Lip

6 weeks

2-3 weeks

5 months


3 weeks

2-3 weeks

5 months


3 months

2-3 weeks

8 months


16 weeks

2-3 weeks

10 months


24 weeks

3-6 weeks

11-12 months

The Three Phases of Hair Growth

a diagram of hairs in different stages of its life cycle

Anagen or "Growth" Phase

This is the phase when the hair is actively growing ​from the follicle.  This is when treatments such as laser and electrolysis are feasible methods of hair removal.  

Cross section of a hair and hair follicle

Cross section of an anagen "growing" hair that's fully attached to the follicle.

Catagen "End of Growth" Phase

At the end of the anagen phase there is an unknown signal that causes the part of the hair follicle that is in touch with the hair to become attached to the hair shaft.  This cuts the hair off from the blood supply - turning it into a club hair.  After the hair is completely converted into a club hair, the telogen phase commences.

Telogen or "Resting" Phase

The telogen phase is simply the resting phase of the hair follicle.  There is no growth during this phase, and this is commonly the stage where dead hairs are shed from the body.  100 hairs fall out on an average person's head each day in the telogen phase.

Interesting Hair Facts

  • Average number of follicles in the human body = 5 million
  • Average total number of hears on the head = 100,000 - 150,000
  • Average percentage of anagen follicles: 90%
  • Average percentage of telogen follicles: 10%

Why is this Important in the Context of Electrolysis and Laser Hair Removal?

Both electrolysis and laser hair removal are only effective when the hair is in the anagen phase, but for different reasons.

Electrolysis and the Anagen Phase

There are a few key factors in a successful electrolysis session:-

  • Hairs need to be visible - in order for the electrologist to be able to successfully treat each individual hair, the hair needs to be visible.  The electrologist needs to insert a hair thin, needle like probe into the hair follicle before applying the electrical current.
  • Salt water based solution in the follicle - Electrolysis works by applying an electrical current into the salt/water based solution that is found at the hair follicle.  The reaction that follows is what disables the hair follicle from being able to grow hair in the future.

When both the above factors are present, electrolysis can be performed and typically the anagen phase is the only phase where this occurs.

Laser Hair Removal and the Anagen Phase

​Laser hair removal works by targeting melanin, a substance responsible for pigment (in both hair and skin), that is only available in abundance during the anagen phase.  

Repeat Treatments are the Only Answer

Given that both electrolysis and laser hair removal are only effective in the anagen phase, repeat treatments are always needed for results.  This is why laser hair removal and electrolysis require repeat treatments for up to a year for the best results.

Cross section of hair

Why Hair Regrowth even after Permanent Hair Removal through Electrolysis is Possible

To make things more complex, the body can activate "new" follicles into hair growth at any point in time.  In reality, these aren't new follicles (they've always existed) but are simply triggered into life at certain points.

Close up of chin stubble

Even after electrolysis, new follicles that weren't active during the treatment can become active, leading to the appearance that old follicles have been reactivated.

Changes in hormone levels is a common trigger for bringing to life a dormant follicle. This is why it's sometimes difficult for the consumer to understand exactly what "permanent" means when it comes to reduction and removal.  Here are some other triggers for hair growth:-

  • Polycystic ovary syndrome
  • Menopause
  • Insulin resistance

While electrolysis is the only method of hair removal that has been approved by the FDA as being "permanent hair removal", it still does not prevent the activation of new follicles that weren't previously active at the time of treatment.  

With that in mind, it's still physically possible to grow new hairs in an area that was treated - they just aren't coming from the previously denatured follicles.​  Of course, to the average consumer, this is not often fully understood, and most salons are not always keen to run through the finer points, of which this is one.

  • Avatar Rafal says:

    What do you mean writing “Cycle Duration” in “Richards-Merhag” table?
    Is this anagen + telogen + catagen?
    Regards Rafal Wenio

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