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How laser hair removal works

Discover hair growth cycles and how the process of laser hair removal works. Find out where you are on the Fitzpatrick scale of skin tone.

Hair growth cycle

Did you know that hair follicles grow in repeated cycles? There are three phases of hair growth every time a new hair is developed, and it’s important to understand that our hair does not grow in unison. While one hair might be in the first stage of hair growth, the one next to it might be in the last; hence one zap of a laser will not get rid of all the hair forever. Each cycle can be broken down into three phases:

  1. Anagen: the active growing stage
  2. Catagen: the transitional stage
  3. Telogen: the resting stage

Hair Growth Cycle
Figure 1 — Hair Growth Cycle

How lasers work on killing hair

Have you ever noticed how dark clothes absorb sunlight and feel warm to the touch? Then you'll begin to understand how the melanin (pigment) within the hair follicle absorbs energy/heat from the laser.

Laser hair removal works by the process of selective photothermolysis. This is when the laser beam is set at a designated wavelength. The laser beam is attracted to the melanin contained within the hair, leaving the surrounding tissue unaffected. The energy from the light beam is converted into heat and travels through the hair shaft and into the hair bulb itself. Here the heat destroys and kills the dermal papilla, which is responsible for feeding the hair bulb and regenerating the hair.

The regrowth of hair will be slower and finer after just two sessions.

Did you know?

Laser hair removal works by directing an intense beam of light at the hair, which is attracted by the melanin (pigment) inside, causing the hair to heat up and the follicle to be destroyed.

Nd: YAG 1064nm laser shot
Figure 2 — Nd: YAG 1064nm laser shot

Anagen

Anagen is considered the growing stage; this is when the root of the hair is the largest, has an abundance of melanin, and is attached to the root. During this phase, the hair grows and becomes visible above the skin. The length of this phase depends on how long that hair will eventually grow; usually at least 2-3 weeks. The Anagen stage is also where the hair is at its darkest pigment, which allows for the best transfer of heat energy from the laser to the hair follicle.

Cross section of Anagen
Figure 3 — cross section of hair during anagen phase

Catagen

Catagen is often called the transition stage. This is a short transitional period in which the hair stops growing and the hair follicle shrinks in size. The follicle breaks away from the dermal papilla that supplies it with nutrients. The dermal papilla then regresses. This stage usually lasts for just a few days.

Cross section of Catagen
Figure 4 — cross section of Catagen hair during catagen phase

Telogen

Telogen is the resting stage. At this stage, laser hair removal is completely ineffective as the hair is not visible and it is fully detached from the root. There is no set time duration for this stage as it can be as short as a week or even longer than a year before it comes back to the anagen phase.

Cross section of Telogen
Figure 5 — cross section of hair during telogen phase

Know your skin tone

The Fitzpatrick scale is a numerical classification for human skin colour based on the response of skin to ultraviolet (UV) light. The Fitzpatrick scale has only six categories.

The Fitzpatrick scale of skin tone
Figure 6 — The Fitzpatrick scale of skin tone
Type Response
I Always burns, never tans.
II Usually burns, tans with difficulty
III Sometimes burns, tans gradually to olive complexion
IV Rarely burns, tans with ease to moderate brown
V Very rarely burns, tans very easily
VI Never burns, tans very easily, deeply pigmented

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