Laser Hair Removal

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How does Laser Hair Removal (LHR) work?

Laser energy is selectively absorbed by the melanin in the hair follicle and converted to heat which diffuses into and injures cells in the hair bulb.

The ideal laser system for hair removal depends on the following parameters:

1.  Wavelength
2.  Pulse width
3.  Effective spot size and fluence (energy)
4.  Cooling (both pre-cooling and parallel cooling)

As wavelength lengthens you will see deeper penetration while a shorter wavelength will result in less penetration (see below).

As wavelength decreases, melanin has a greater absorption and as wavelength increases, absorption for melanin decreases (see curve below - brown line).  More absorption means more heating which translates to more effective destruction of the hair follicle.


The optimal wavelength for LHR is 750-850 nm as this represents the best balance of absorption and penetration.

The Ruby wavelength (694 nm) is too well absorbed by melanin to treat darker skin patients as surface melanin may cause burning of the skin (epidermis).  The Nd:YAG laser (1064 nm), because of lower melanin absorption, requires 3-4x's the fluence (energy) for similar effects.  This causes more pain, decreased efficacy and increased number of treatments needed for optimal results.  The decreased melanin absorption and increased depth of penetration makes the Nd:YAG the laser of choice for spider veins.

The Alexandrite laser (755 nm) is effective for LHR but is only safe to use in skin types I-III.  Here at Lower Salford Laser we use the Sonata Diode Laser 810 nm.  This provides excellent results and is approved for skin types I-VI.

Pulse Width
The pulse width represents the speed at which the energy is released into the skin.  With the Sonata, the pulse width can be increased to allow slower heating of the melanin in the hair follicle, preserving the melanin in the epidermis and thus making it a safe option of darker skin colors.

Effective Spot Size and Fluence
As fluence is increased, more heat is generated and more effective hair removal takes place.  This is limited by patient's skin type (darker the skin, the lower the fluence that can be used).  This is also the reason why it is recommended that you do not tan during treatment as fluence will need to be decreased as your skin darkens thus slightly decreasing the efficacy of treatment.  Spot size relates to speed of treatment of larger areas.  The Sonata has a large 12 x 10 mm spot size allowing for quicker treatments of larger areas.

Cooling of the skin is very important as it prevents damage to the epidermis by melanin absorption above the hair bulb.  Cooling also provides patient comfort.  Here at Lower Salford Laser we use the popular Zimmer Cooler in conjunction with the laser to increase your comfort.  The Sonata comes with contact cooling as well.

How many treatments do I need?

Most people with laser hair removal will need 4-6 treatments for effective results.  As the laser targets melanin, those with darker, coarser hair will achieve the best results per individual treatment.  The lower the skin type also allows maximal use of laser energy to heat the hair bulb as there is decreased concern of heating the epidermis and causing a burn.  Multiple treatments are needed as laser hair removal is most effective in the active (Anagen) phase of hair growth and not all of your hair is in this phase at any one time.  (see below)

Hair Growth Phases:
1.  Anagen Phase (active)
2.  Catagen Phase (intermediate)
3.  Telogen (shedding)

In the anagen phase, hair growth is active and melanin is being produced in the hair bulb at the base of the hair.  This allows maximal heating of the hair follicle and arrest of hair growth.  During the catagen phase, no hair growth or pigment production occurs.  The telogen phase of the hair cycle is marked by the formation of a new hair in the follicle which causes the shedding of the hair.  The hair follicle then recycles back to the anagen phase.

As length of cycles varies by body area (facial hair typically being shorter than body hair), your interval between treatments will vary based on the treatment area and an individual's own hair growth velocity.  Typically intervals will be 4-6 weeks for facial areas and 6-8 weeks for body areas.  Intervals will also lengthen as you progress in you treatments and have hair reduction and decreased speed of growth.

How Does an IPL (Intense Pulse Light) Compare with Laser?

IPL's use a range of wavelengths where as a Laser is a single wavelength of light.  The range of wavelengths causes IPL's to have more scatter and collateral damage.  If you have seen pictures of rectangular scars secondary to light therapies, these represent treatments from an IPL as their spot sizes are much larger.  They also do not achieve the same fluence (energy) as lasers.  This requires IPL's to need more treatments for effective hair removal (typically 6-10 treatments) to LHR (typically 4-6 treatments).  This causes a total treatment price to often be more expensive with IPL's.  IPL's used properly can be very effective for skin blemishes and other uses but will always be less effective than laser for hair removal.

If you have any questions regarding laser hair removal please call us at (215) 256-8040 or email us at