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Hair removal laser treatment

Introduction to laser hair removal

Laser hair removal is currently most popular due to its fast, safe and successful treatments, giving long-term benefits. Numerous studies have corroborated their superiority. However, it has been largely confined to removing dark hairs of fair people. New laser techniques to treat dark patients have now been developed and are expected to be deployed soon. What remains is the treatment of light hairs which also will, hopefully, be available in the not too distant future.

Laser devices

Laser hair removal employs the principle of selective photothermolysis and uses several devices for the purpose. The targeted chromophore may be endogenous like, melanin in the hair or exogenous like carbon particles introduced in the skin.

Devices that target melanin are those which produce wave lengths absorbed by melanin. These are 694nm long pulse ruby lasers, 755nm long pulse alexanderite lasers, 800nm pulse diode lasers, 1064nm Q-switched Nd:YAG lasers and 590 to 1200nm intense pulse lasers or IPL. Devices that target exogenous chromophores are carbon particles + 1064nm Q-switched Nd:YAG lasers and 5-Aminolevulinic acid.

Melanin pigment

By targeting the melanin in the hair, selective destruction of various parts of the hair follicle is possible. However, the melanin in the skin may also absorb laser radiation causing skin damage. Such epidermal damage can be limited by using appropriate cooling means like, ice, cooled gel layer and many other devices.

Laser pulse width seems to be critical for the kind of hair removal desired, that is, short or long term. Over the years, pulse widths have increased from nanoseconds through microseconds to milliseconds. Trials have revealed that short pulse lasers like, Q-switched Nd: YAG lasers rapidly heat up the melanin, releasing photoacoustic shock waves which disturb the melanocytes but achieve incomplete follicular destruction. This incomplete destruction of the follicle fails to achieve permanent hair removal. However, short pulse widths in the milliseconds range can remove hair temporarily.

Sometimes, for hair removal, the targets are unpigmented, such as, follicular stem cells that do not have melanin in them. And since without melanin there cannot be any light absorption, the nearby pigmented hair shaft is targeted. In such cases, long pulse widths have been suggested to allow time for the heat to spread in the entire hair volume to bring about stem cell damage. Super long pulses, greater than 100 microseconds, appear to cause long term hair removal.

The fluence used also plays a role in the success of hair removal. High fluences cause higher hair removal. The patient’s skin related factors determine the optimal fluence that results in hair removal without any damage.

Exogenous chromophore

The problem of unwanted absorption of light energy by the skin melanin is resolved by introducing external chromaphores whose light absorption level is different from melanin. The difficulty here is about introducing the chromophore equally at all depths of the follicule.

The soft light system uses carbon particles as chromophores. A suspension of carbon particles is applied on a wax-epilated skin. The suspension is then removed and the skin irradiated by a relatively low energy Q-switched Nd:YAG laser. While hair regrowth is significantly delayed by this method, compared to laser alone treatment there are no extra benefits.

PDT, using 5-ALA photosensitizer and 630nm argon pumped tunable dye laser underwent trial in a small pilot study. Dose dependent decrease in hair regrowth was observed. The potential benefit of PDT perhaps lies in the action of photosensitizers in the hair follicles. Because photosensitizers tend to localize in the follicular epithelium, potentially, hairs of all colors and in all stages of the growth cycle could be destroyed.

Pre-operative care

A complete history of hypertrichosis, herpes labialis if the perioral area is involved, herpes genitalis if the pubic area is to be treated, and history of previous treatments will be needed by the surgeon. Six weeks before treatment the patient should avoid all kinds of hair removal, except shaving. During treatment, hair loss from the shaved area is higher than from epilated areas. If sun exposed sites are involved, then sun exposure of those sites should be avoided. All body sites can be treated but treatment on or around the eye is not advised.

Side effects of laser hair removal

Laser treatment is not painless. All patients feel some pain during and immediately after treatment. A topical or local anesthetic may be used to reduce pain. Perifollicular erythema and edema occurs in all cases and usually last up to 3 days. Excessive fluences may cause skin damage. Herpes simplex and infections are rare. Temporary pigmentation changes and hyperpigmentation can occur but are more common in dark skinned patients as is permanent pigmentary changes. Tattoo lightening and freckle loss is possible.

 

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