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Laser Hair Removal (continued)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 Ruby: 694 nm Alexandrite: 755 nm Pulsed diode array: 810 nm Nd:YAG: 1064 nm Pulsewidth is an important consideration. It has been observed in some published studies that longer pulsewidths are safer in darker skin. Wavelength is a critical factor. Longer wavelengths are safer in darker skin.
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 mm). 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, especially in darker skin. 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: forced cold air at -34 degrees C (Zimmer Cryo 5 unit) 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 at 1 month for the face, 2 months for the chest and 3 months for the legs. 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, this 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. 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.
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