Epilation by laser was performed experimentally for about 20 years before it became commercially available in the mid 1970s. Intense Pulsed Light (IPL) epilators, though technically not a laser, use xenon flash lamps that emit full spectrum light. Laser and light-based methods, sometimes called phototricholysis or photoepilation, are now most commonly referred to collectively as "laser hair removal". One of the first published articles describing laser hair removal was authored by the group at Massachusetts General Hospital in 1998.[1][2]
The efficacy of laser hair removal is now generally accepted in the dermatology community, and laser hair removal is widely practiced. Many reviews of laser hair removal methods, safety, and efficacy have been published in the dermatology literature.[3]
Monday, October 25, 2010
Mechanism of action
The primary principle behind laser hair removal is selective photothermolysis (SPTL).[4] Lasers can cause localized damage by selectively heating dark target matter, (melanin), in the area that causes hair growth, (the follicle), 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 melanin:
* Melanin is considered the primary chromophore for all hair removal lasers currently on the market. Melanin occurs naturally in the skin (it gives skin and hair its color). There are two types of melanin in hair: eumelanin (which gives hair brown or black color) and pheomelanin (which gives hair blonde or red color). Because of the selective absorption of photons of laser light, only black or brown hair can be removed.
Laser works best with dark coarse hair. Light skin and dark hair are an ideal combination, but new lasers are now able to target dark black hair even in patients with dark skin.[5]
Hair removal lasers have been in use since 1997 and has been approved for "permanent hair reduction" in the United States by the Food and Drug Administration (FDA).[6] "Permanent" hair reduction is defined as the long-term, stable reduction in the number of hairs re-growing after a treatment regime. Indeed, many patients experience complete regrowth of hair on their treated areas in the years following their last treatment. Laser hair removal has become extremely popular because of its speed and efficacy, although some of the efficacy is dependent upon the skill and experience of the laser operator, and the choice and availability of different laser technology at the clinic which is performing the procedure. Some will need touch-up treatments, especially on large areas, after the initial set of 3-8 treatments. It has also been observed that some people seem to be non-responders – this is not confirmed and reasons are not known, and may in fact be due to lack of skill on the part of many laser operators and/or the type of machine and settings they are using.[7]
Hair removal lasers selectively target melanin:
* Melanin is considered the primary chromophore for all hair removal lasers currently on the market. Melanin occurs naturally in the skin (it gives skin and hair its color). There are two types of melanin in hair: eumelanin (which gives hair brown or black color) and pheomelanin (which gives hair blonde or red color). Because of the selective absorption of photons of laser light, only black or brown hair can be removed.
Laser works best with dark coarse hair. Light skin and dark hair are an ideal combination, but new lasers are now able to target dark black hair even in patients with dark skin.[5]
Hair removal lasers have been in use since 1997 and has been approved for "permanent hair reduction" in the United States by the Food and Drug Administration (FDA).[6] "Permanent" hair reduction is defined as the long-term, stable reduction in the number of hairs re-growing after a treatment regime. Indeed, many patients experience complete regrowth of hair on their treated areas in the years following their last treatment. Laser hair removal has become extremely popular because of its speed and efficacy, although some of the efficacy is dependent upon the skill and experience of the laser operator, and the choice and availability of different laser technology at the clinic which is performing the procedure. Some will need touch-up treatments, especially on large areas, after the initial set of 3-8 treatments. It has also been observed that some people seem to be non-responders – this is not confirmed and reasons are not known, and may in fact be due to lack of skill on the part of many laser operators and/or the type of machine and settings they are using.[7]
Comparison with electrolysis
Electrolysis is another hair removal method that has been used for over 135 years.[8] At this time, it is the only permanent option for very fine and light-colored hair. The FDA currently allows the term "Permanent Hair Removal" for electrolysis only. Unlike laser epilation, electrolysis is effective on all hair colors.
A study conducted in 2000 at the ASVAK Laser Center in Ankara, Turkey comparing alexandrite laser and electrolysis for hair removal on 12 patients concluded that laser hair removal was 60 times faster, less painful and more reliable than electrolysis.[9]
A study conducted in 2000 at the ASVAK Laser Center in Ankara, Turkey comparing alexandrite laser and electrolysis for hair removal on 12 patients concluded that laser hair removal was 60 times faster, less painful and more reliable than electrolysis.[9]
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 nm (DeepSkyBlue) or 514.5 nm (Cyan) (no longer used for hair removal)
Ruby laser: 694.3 nm (OrangeRed) (no longer used for hair removal; only safe for patients with very pale skin) [10]
Alexandrite: 755 nm (Red) (most effective on pale skin and not safe on darker skin at effective settings)
Pulsed diode array: 810 nm (Near-Infrared) (for pale to medium type skin)
Nd:YAG laser: 1064 nm (Near-Infrared) (made for treating darker skin types, though effective on all skin types)
Pulse width is an important consideration. Longer pulse widths may be safer for darker skin, but shorter pulsewidths are more effective in disabling hair follicles.[citation needed] Repetition rate is believed to have a cumulative effect, based on the concept of thermal relaxation time.[citation needed] 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. This may increase the "kill rate" for each treatment.
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. Hair removal lasers have a spot size about the size of a fingertip (8-18mm). Larger spot sizes help laser light penetrate deeper and make treatments faster and more effective.
Fluence or energy level is another important consideration. Fluence is measured in joules per square centimeter (J/cm²). It's important to get treated at high enough settings to heat up the follicles enough to disable them from producing hair.
Epidermal cooling has been determined to allow higher fluences and reduce pain and side effects, especially in darker skin. Three types of cooling have been developed:
* Contact cooling: through a window cooled by circulating water or other internal coolant
* Cryogen spray: Sprayed directly onto the skin immediately before and/or after the laser pulse
* Air cooling: forced cold air at -34 degrees C (Zimmer Cryo 5 unit)
Argon: 488 nm (DeepSkyBlue) or 514.5 nm (Cyan) (no longer used for hair removal)
Ruby laser: 694.3 nm (OrangeRed) (no longer used for hair removal; only safe for patients with very pale skin) [10]
Alexandrite: 755 nm (Red) (most effective on pale skin and not safe on darker skin at effective settings)
Pulsed diode array: 810 nm (Near-Infrared) (for pale to medium type skin)
Nd:YAG laser: 1064 nm (Near-Infrared) (made for treating darker skin types, though effective on all skin types)
Pulse width is an important consideration. Longer pulse widths may be safer for darker skin, but shorter pulsewidths are more effective in disabling hair follicles.[citation needed] Repetition rate is believed to have a cumulative effect, based on the concept of thermal relaxation time.[citation needed] 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. This may increase the "kill rate" for each treatment.
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. Hair removal lasers have a spot size about the size of a fingertip (8-18mm). Larger spot sizes help laser light penetrate deeper and make treatments faster and more effective.
Fluence or energy level is another important consideration. Fluence is measured in joules per square centimeter (J/cm²). It's important to get treated at high enough settings to heat up the follicles enough to disable them from producing hair.
Epidermal cooling has been determined to allow higher fluences and reduce pain and side effects, especially in darker skin. Three types of cooling have been developed:
* Contact cooling: through a window cooled by circulating water or other internal coolant
* Cryogen spray: Sprayed directly onto the skin immediately before and/or after the laser pulse
* Air cooling: forced cold air at -34 degrees C (Zimmer Cryo 5 unit)
Number of sessions
Multiple treatments (typically 6-8 spaced 8-12 weeks apart) depending on the type of hair and skin color have been shown to provide long-term reduction of hair. Current parameters suggest a series of treatments spaced at 8-12 weeks apart for based on typical hair cycle patterns for each area.[11]
The number of sessions depends on various parameters, including the area of the body treated, skin color, coarseness of hair, reason for hirsutism, and sex. Coarse dark hair on light skin is easiest to treat. Hair on darker skin is harder to treat. Finer hair is only sometimes affected. Certain areas (notably men's faces) may require considerably more treatments to achieve desired results. In addition, since hair grows in several phases (anagen, telogen, catagen) and laser can only affect the currently active growing follicles (anagen), several sessions are needed to kill hair in all phases of growth.
It's important to note that laser does not work well on light-colored hair and most fine and vellus hair ("peachfuzz") of any color
The number of sessions depends on various parameters, including the area of the body treated, skin color, coarseness of hair, reason for hirsutism, and sex. Coarse dark hair on light skin is easiest to treat. Hair on darker skin is harder to treat. Finer hair is only sometimes affected. Certain areas (notably men's faces) may require considerably more treatments to achieve desired results. In addition, since hair grows in several phases (anagen, telogen, catagen) and laser can only affect the currently active growing follicles (anagen), several sessions are needed to kill hair in all phases of growth.
It's important to note that laser does not work well on light-colored hair and most fine and vellus hair ("peachfuzz") of any color
Intervals between sessions
Usually treatments are spaced 8–12 weeks apart depending on the body area and the hair cycle length for that area. For example, faces usually require more frequent treatments about 3-4 weeks apart, whereas legs require less frequent treatments.
Instead of following an arbitrary schedule, one should wait until they have experienced shedding of the treated hairs, which should complete within 2-3 weeks, and see enough hair come in after the hair-free period to have another treatment.[12] It's advisable to do a touchup if significant amount of hair hasn't shed within 3 weeks.
Instead of following an arbitrary schedule, one should wait until they have experienced shedding of the treated hairs, which should complete within 2-3 weeks, and see enough hair come in after the hair-free period to have another treatment.[12] It's advisable to do a touchup if significant amount of hair hasn't shed within 3 weeks.
Other uses
Hair removal lasers are effective treatment for pseudofolliculitis barbae (commonly called ingrown hairs or "shaving bumps"). For darker skin patients with black hair, the long-pulsed Nd:YAG laser with a cooling tip can be safe and effective when used by an experienced practitioner.
They have recently been reported as helpful treatment for pilonidal cysts, since they eliminate the ingrown hairs that produce the troublesome foreign body reactions in this congenital malady.
They have recently been reported as helpful treatment for pilonidal cysts, since they eliminate the ingrown hairs that produce the troublesome foreign body reactions in this congenital malady.
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