Epilation performed by laser was performed experimentally for about 20 years before it became commercially available in the mid 1990s. Laser and light-based methods are sometimes called phototricholysis or photoepilation.
Laser Hair Removal
In Addition to Lasers, some light-based epilators use a xenon flashlamp which emits full-spectrum intense pulsed light (IPL). Treatment with this device is sometimes popularly referred to as laser hair removal, though the device is not a laser per se.
The primary principle behind laser hair removal is selective photothermolysis. Lasers can cause localized damage by selectively heating dark target matter in the area that causes hair growth while not heating the rest of the skin. Light is absorbed by dark objects, so laser energy can be absorbed by dark material in the skin (but with much more speed and intensity). This dark target matter, or chromophore, can be naturally-occurring or artificially introduced.
Hair removal lasers selectively target one of three chromophores:
- Carbon, which is introduced into the hair follicle by rubbing a carbon-based lotion into the skin following waxing (this lotion is an “exogenous chromophore”). When irritated by an Nd:YAG laser, the carbon causes a shock wave capable of mechanically damaging nearby cells.
- Hemoglobin, which occurs naturally in blood (it gives blood its red colour). It preferentially absorbs wavelengths from argons, and to a lesser extent from rubies, alexandrites and diodes. It minimally absorbs the Nd:YAG laser wavelength.
- Melanin is considered the primary chromophore for most lasers currently on the market. Melanin occurs naturally in the skin (it gives skin and hair its colour). There are two types of melanin in hair: eumelanin (which gives hair brown or black colour) and pheomelanin (which gives hair blonde or red colour).
Laser Parameters That Affect Results
Several wavelengths of laser energy have been used for hair removal, from visible light to near-infrared radiation. These lasers are usually defined by the lasing medium used to create the wavelength (measured in nanometers (nm) ):
- Argon: 488 or 514.5 nm wavelength
- Ruby: 694 nm wavelength – Long Pulse mode
- Alexandrite: 755 nm wavelength – Long Pulse mode
- Pulsed Diode Array: 810 nm wavelength – Long Pulse mode
- Nd:YAG: 1064 nm wavelength – Long Pulse mode
Pulsewidth is an important consideration. It has been observed in some published studies that longer pulsewidths may be more effective with fewer side effects. Recently, very long pulse or super long pulse lasers have been theorized to be safer for darker skin, but this has yet to be demonstrated in published data.
Spot size, or the width of the laser beam, affects treatment. Theoretically, the width of the ideal beam is about four times as wide as the target is deep. Most lasers have a round spot about the size of your little finger (8-10 nm).
Fluence or energy level is another important consideration. Fluence is measured in joules per square centimeter (J/cm2).
Repetition rate is believed to have a cumulative effect, based on the concept of thermal relaxation time. Shooting two or three pulses at the same target with a specific delay between pulses can cause a slight improvement in the heating of an area.
Epidermal cooling has been determined to allow higher fluences and reduce pain and side effects. Four types of cooling have been developed:
- Clear gel: usually chilled
- Contact cooling: through a window cooled by circulating water
- Cryogen spray: immediately before/after the laser pulse
- Air cooling: a newer experimental method
Multiple treatments have been shown in numerous studies to be more effective for long-term reduction of hair. Current parameters suggest a series of treatments spaced 4 to 6 weeks apart, but theoretically, there is a point of diminishing return where additional treatments will not cause additional loss.
Laser energy also gets less effective the deeper into the skin it must travel. Think of it like putting your hand over a flashlight. A little light penetrates the thinner skin (the reddish glow), but can’t penetrate the thicker areas. Light that enters the skin is either absorbed or scattered and reflected back out of your hand. When this happens to a laser beam, the scattering is called attenuation. The more tissue light has to travel through, the more attenuation will occur. That means at deeper levels, less energy reaches the target.
The Ruby laser is the pioneer of the range. It was manufactured in 1960, and produces a red light with a wavelength of 694 nm. Originally, it was mainly used in retinal surgery. The Ruby laser light is mostly absorbed by blue and black pigment and by the melanin in the skin and hair. Although very efficient, it also displays three (3) inconveniences: this piece of equipment is quite large, it has a fairly high maintenance cost, and the risks of creating white spots on the skin remain a possibility.
Proud successor of the Ruby laser, the Alexandrite laser produces a deep red light at 755 nm, allowing for a slightly deeper skin penetration than the Ruby laser. Widely used with very good clinical results, it is fast in treatment execution. These lasers lead to de-pigmentation, and the cost is relatively high. The pulse mode is mainly used for hair removal functions while the Q-switched mode is used for tattoo removal.
The familiar “laser pointers” are in fact diode lasers. Born in 1998, providing a wavelength range of 800 to 900 nm, widely spread across the world, this laser is definitely very popular in the hair removal market. Its wavelength allows to treat any skin type, and it combines a nice balance between usage parameters, reliability and compact sizing (portable).
Yag Laser and Nd: YAG Laser
This was the first laser that was approved by the FDA. It has however, misfired but is now rising from its ashes. The laser now offers a longer pulse time, and allows treatment on dark or tanned skin types while limiting the inherent risks. A longer pulse time however, translates into a little more painful treatment. All YAG lasers may be operated in continuous/pulsed or Q-switched mode. This laser is also referred to as the workhorse and typically emits an invisible light with a wavelength of 1064 nm, in the infrared.
Nd: YAG is an acronym for Neodymium-doped Yttrium Aluminum Garnet, a compound that is used as the lasting medium for certain solid-state lasers. However, there are also transitions near 940, 1120, 1320, and 1440 nm.
Other common host materials for neodymium are: YLF (yttrium lithium fluoride, 1047 and 1053 nm), YVO (yttrium vanadate, 1064 nm), and glass. A particular host material is chosen in order to obtain a desired combination of optical, mechanical, and thermal properties. Nd: YAG lasers and variants are pumped either by flash lamps, continuous gas-discharge lamps, or near-infrared laser diodes. Prestablized laser (PSL) types of Nd: YAG lasers have proved to be particularly useful in providing the main beams for gravitational wave interferometers such as LIGO, VIRGO, GEO600 and TAMA.
For many applications, the infrared light is frequency-doubled or -tripled in order to obtain visible (527 or 532 nm, green) or ultraviolet light.
Other Photo-Depilation Methods
- IPL Flash Lamp (Intense Pulsed Light)
Intense Pulsed Light (IPL) is a method of permanently removing hair from the body involving the use of a specially constructed xenon flash lamp and focusing optics. The flash lamp is linked to a computer controlled power source, and should be said that the system is not a real laser because its light is non coherent. The light is actually diffused through coloured filters, which intensity may be adjusted to treat any skin type and very precisely target a lesion. Its wider spectrum favours good light absorption by melanin.
The focused, broad spectrum light is applied to the surface of the skin by way of either a hand-held wand, or by an articulated arm. The intense light travels down the hair shafts, where it strikes the bulb, or root, of the hair. The bulb is usually where the highest concentration of melanin is located, as opposed to the rest of the hair shaft.
When the light strikes the dark-coloured melanin, the light is converted to heat energy. The bulb and most of the hair shaft is instantly vaporized. The intense heat radiated by the hair also destroys the hair-producing papilla or the entire hair follicle. It is also claimed that direct light-heat conversion occurs directly in the darker coloured capillaries that bring nourishing blood to the follicle.
The pulses of light produced IPL equipment are very short in duration, so discomfort and damage to non-target tissues is very minor. Most people who undergo IPL epilation, only experience slight irritation similar to that of a minor sunburn. The light that eminates from the IPL wand is filtered to remove any ultraviolet components, eliminating the possibility of UV skin damage.
The end result of epilation using IPL is a mass of dead hair follicles and invisible, sub-dermal scar tissue.
The IPL process has become quite popular due to the low cost of equipment and service rates of IPL practioners, as well as the very rapid procedure. IPL purportedly compares to laser hair removal, which sometimes can be costlier due to the fewer treatments needed for successful hair removal. The comparison of effectiveness between IPL and laser epilation is debated by scientists, equipment manufacturers and practitioners. Although this method is affordable, the lamp needs to be replaced on a relatively frequent basis, therefore requiring equipment recalibration as well.
IPL is also used for the treatment of rosacea, skin pigmentation, broken capillaries and freckles.
RF (Radio Frequency) combined to an IPL (Intense Pulsed Light)
This process combines Intense Pulsed Light (IPL) and electric energy (RF or radio frequency). It increases hair follicle heat using IPL and uses RF to eliminate germinal cells. It is also said that this technology offers the advantage of treating poorly pigmented hair while limiting secondary (according to ELOS – Electro Optical Synergy). Note that this method, just like IPL alone, considerably diffuses heat in a group of tissues, without selectively targeting hairs. It also provides the possibility of treating any skin type.
Radio Frequency can be used in association with IPL, or, with laser sources to optimize constant heat effect in the hair follicle. However, results on white hair have not yet been established and current clinical results are not up to expectations and propaganda.
Many questions must be answered before buying a system that will adequately fulfill a clinic’s specific needs. What kind of power is needed? Which wavelength is best? What should be the size of that wavelength? Determining a budget is also a priority. Prices vary in accordance with elements such as components, precision, laser purity, beam direction, stability and power. In order to make a proper choice many points should be verified, amongst many, the technical data of a device. Each device however, is characterized by multiple nuances. For this reason, it is extremely difficult for the future user, without adequate training, to understand the range of each of these elements:
- The technology used
- The parameterization system
- The power:
- The device and power output delivery for the hand piece
- Power output by pulsation
- Pulsation period in relation to parameterization
- The skin cooling system offered
- The hand piece
- Anti-release system
- Its treatment surface
- Security system
- Maintenance requirements