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How lasers work on killing hair

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:

hair growth cycle 01

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

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 photo thermolysis. 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.

Anagen (active growth stage)
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.

Catagen (cells stop growth/transitional stage)
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.

Telogen (follicle inactivity/resting stage)
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.

For laser hair removal to be successful, you must zap hairs in the Anagen growth stage!