Science of Laser Hair Removal
The human pigment melanin is the target chromophore found in human skin that selectively absorbs light energy from hair removal lasers. Different types of lasers are needed to treat different types of skin and hair. Hair removal lasers operate at different wavelengths on the electromagnetic spectrum because some are better at treating darker tones and some are better at treating finer hairs. An early laser that is not commonly used today is the Ruby laser. Ruby laser light, which operates at wavelength 694 nm, is so intensely absorbed by melanin that it significantly limits its ability to treat a broad range of skin and hair types. This is due to the competing melanin in the skin. Consequently, this laser is mainly limited to very fair-skinned individuals. It is, though, quite effective in treating fine hairs. The newer Nd:YAG laser operates at 1064 nm, which has an absorptive spectrum of melanin that provides the ability to treat even the darkest skin tones. The Nd:YAG cannot treat fine hairs as accurately, and is more effective against coarser textures of hair. The Alexandrite Laser, at 755 nm, and the Diode Laser, at 810 nm, are widely used and may treat a variety of individuals, except for the darkest skin tones. Overall, this laser light energy is converted to thermal energy in the follicle. The follicle structures such as the bulge and papilla are then damaged and/or destroyed by the heat.
Pulse duration, fluence, and spot size are also extremely important factors in laser hair removal. Pulse duration is the length of time that energy from the laser is applied to the target. Longer pulse durations allow the skin to heat up more slowly and are safer for darker skin tones. Shorter pulse durations can be more effective for treating fine and light colored hair. Different lasers offer varying ranges of pulse duration.
Fluence is the amount of energy delivered to a given area. The goal is to achieve a high enough fluence to destroy the key follicle components without damaging surrounding skin. Higher fluences achieve better results, but also at the risk of greater thermal damage (burns or pigment changes).
The spot size is the area that a laser is capable of treating with each pulse. Effective hair removal requires at least 3-5 mm. Spot sizes and the depth of penetration have a positive correlation; the larger the spot size, the greater the depth of penetration, providing for more effective results with less risk of thermal damage. Higher fluences may be used with smaller spot sizes, although the depth of penetration is less. Lasers for hair removal limit the amount of energy that can be used with the larger spot sizes, but an advantage is the greater depth of penetration for follicles that are deeper.
With over 70 different lasers on the market for hair removal, intricate understanding of physiology, medical factors, and laser physics is crucial in performing procedures. Because lasers offer many different choices and settings for wavelength, pulse duration, fluence, and spot size, an experienced and highly trained physician at Cosmetic Laser Solutions performs all procedures.
Since a high level of heat is necessary to destroy the hair follicle, there are cooling mechanisms in lasers to prevent damage to the surrounding tissue. If a chromophore, such as melanin, is heated beyond its capacity, the heat may diffuse into the surrounding structures and severe burns or pigment changes may result. Cooling mechanisms not only prevent damage to the skin and its structures, but also provide for a more comfortable treatment experience with lower levels of pain and swelling while allowing the skin to be treated at higher levels for maximum results. There are several different types of cooling mechanisms that may be used with lasers.
Cryogen spray is a widely used method that delivers a cooling spray before and/or after every laser pulse. It is consistently very effective and easy to use, but the cryogen may be expensive. It is also possible to freeze or blister the skin if too much is used (cryogen is between -30 and -50° C), and it is even possible for it to hinder the effects of treatment if not used properly.
Air cooling is also an effective method of cooling, but requires a very large stand-alone machine, whereas cryogen may be built into the laser. Air cooling can be somewhat less consistent in the amount of cooling with each laser pulse.
Contact cooling is effective, but requires a very experienced operator and can be difficult to use. It consists of a cold, gliding hand-piece used over a gel.
Cooling gels, the least effective cooling mechanisms, are applied before and/or after treatment, and only provide short-term effectiveness. They are messy to use and can easily be applied unevenly, therefore leading to inadequate cooling of the tissue.
Most lasers use contact, cryogen, or air cooling since these mechanisms offer minimal adverse effects with more consistent results. Some of the mechanisms are much more difficult to use and require an experienced physician. Dr. Goldboss has performed over 10,000 laser procedures and continues to perform all the procedures at Cosmetic Laser Solutions.
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