How Do Lasers Work?

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Lasers deliver an intense beam of light which are made up of a single wavelength or colour. Skin is essentially transparent to light in the wavelength range of 600 - 1100nm (nano meters), while melanin containing structures will absorb laser energy of this wavelength. It is therefore possible to target the hair follicle which has a concentration of melanin without affecting the surrounding area.

The light energy absorbed by the melanin pigment results in the rapid heating up of the hair follicle. This heat destroys the cells (papilla) responsible for hair growth. If adequate heating is achieved, then the follicle is permanently disabled resulting in a permanent reduction in hair growth.

Suitable Skin Types

Melanin in the epidermis also absorbs the energy and limits the depth of penetration of the laser light into the skin. Using a light wavelength of 808nm enables treatment of relatively dark skin as well as fair-skinned types. However, laser hair treatment is not suitable for Afro Caribbean or black skin complexions. Laser treatment is also ineffective in removal of white or grey hair. Electrolysis should be considered as an alternative treatment.

As a guide skin colours are classified by the Fitzpatrick skin prototypes. The classification is as follows:

Skin Type	Skin Colour	Tanning History	Maximum Power Level
I	very fair "transparent"	always burns, never tans	All laser power levels should be suitable
II	fair	always burns, tans with difficulty
III	fair to light olive	burns mildly, tans slowly
IV	olive to brown	rarely burns, tans with ease	Up to level 3
V	dark brown	very rarely burns, tans very easily	NOT suitable for Laser Hair Removal
VI	black	never burns, tans very easily	NOT suitable for Laser Hair Removal

Why is a series of treatments required?

Everyone's hair grows differently, depending on age, weight, metabolism, hormones, ethnicity, medications and other factors. But all hair goes through three distinct growth phases:

Active growth phase (called the anagen phase), which lasts between 2 and 7 years. During this phase the dermal papilla actively produces cells which form the hairshaft. In certain areas of the body, such as the scalp, the majority (83%) of the hairs are in this phase. During the anagen phase the hair has an abundance of melanin.

Degradation phase (catagen phase), which lasts between 10 and 20 days, during which the hair stops growing but is not yet shed. About 3-4% of our body hair is in this phase at any given time. The hair follicle shrinks at this time as the hair is prepared for eviction.

Resting phase (telogen phase), which can last for several months, during which the hair falls out and a new hair begins to form. The hair follicle is not treatable during this time.

Laser treatment is only effective when the hair is in the active growth phase. Hairs or hair follicles in the Degradation or Resting phase need to progress to the active phase before treatment will be beneficial. Therefore, multiple treatments are required for long term, permanent hair reduction.

Also, in a single treatment, not all of the hair follicles in the active phase will be destroyed. Some follicles are destroyed, others may be miniaturised into vellus hairs (light, fine hairs), and some enter prolonged dormancy. The initial treatment should be repeated to take care of active hair follicles that were not effectively treated in the first session as new hair growth is observed, this will typically be some 2 to 4 weeks later depending on where the treatment area is. Further treatments should be planned at regular intervals to clear hairs that are coming out of the resting phase and into the active growth phase. Given the number of hair follicles in the resting phase at any given time, this new hair re-growth can be significant.

Any follicles without a target hair within will simply grow again and can be treated next time round.

Body Site	Follicle Density (per square cm)	Resting Phase	Time in Resting Place	Active Growth
Head	350	15%	3 months	83%
Arms	80	18%	5 months	79%
Legs	60	18%	6 months	79%
Beard	500	68%	10 weeks	30%
Upper Lip	350	64%	6 weeks	34%
Armpit	65	28%	3 months	69%
Chest/Back	70	28%	3 months	69%
Pubic	70	25%	3 months	71%

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