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How Light Can Be Used To Remove Unwanted Hair
Light at specific wavelengths can be used to destroy hair. Melanin is
a pigment found in the hair shaft and serves as the target. When melanin
in the hair shaft absorbs the light, the energy in light is converted
into heat. The heat can then be transmitted down the hair shaft to the
root causing injury or destruction of the hair. The source of the light
can be a laser that operates in the red to near infrared wavelength region.
It can also come from a specialized flash lamp (Intense Pulsed Light)
that utilizes filters, which eliminate shorter wavelengths. This allows
only longer more penetrating wavelengths to be emitted. Intense Pulsed
Light (IPL) allows for a wide choice of wavelengths, which makes the device
effective in treating a wide range of skin types (light to dark skin).
One of the challenges in photomedicine is to be able to destroy the target
(hair) in all skin types but not injure the skin. The potential for injury
exists because the epidermis contains melanin (the amount varying according
to the skin color). Melanin in the skin can compete with the melanin in
the hair follicles for absorption of light energy. If melanin in the skin
were to absorb significant amounts of light energy, the epidermis could
be injured. This problem can however, be prevented by the judicious selection
of the proper wavelength, which alters the penetrating distance of the
light and the selective cooling of the epidermis. The device that I have
selected is the Palomar MediLux IPL, which offers an unsurpassed selection
of wavelengths as opposed to laser, which offers only one wavelength.
The IPL utilizes a sapphire hand piece that is cooled between 0 and 10
degrees Celsius. The hand piece is put in direct contact with the skin,
which provides a heat conduction pathway away from the epidermis before,
during and after each pulse of light is administered. This combined approach
prevents any significant thermal injury to the epidermis.
There are three phases in the life cycle of a hair. They are Anagen (the
active phase of hair growth), Catagen (a transition phase when cell division
ceases) and Telogen (a resting phase during which the hair follicles detach
and fall out). Light therapy is only effective when the hair is in the
Anagen phase (ie: active cell division is taking place). On any given
body part at any given time, a variable amount of hair is in Anagen. Hair
is most vulnerable to injury at this time, because this is when cell division
(mitosis) is taking place. One application is not likely to be completely
successful because not all hair is in Anagen at the same time and a repeat
application will be necessary when the hair follicles once again enter
into Anagen. This can be recognized by the early regrowth of hair. The
duration of each phase can vary from one part of the body to the next,
but this usually occurs in 6-8 weeks. On average, about four to six applications
are necessary to achieve the best results.
Melanin is absent in blond, red and gray hair and therefore it is very
difficult to destroy hair of these colors. Patients with darker skin have
more melanin in their epidermis and therefore hair removal, although possible,
is somewhat more difficult. The ideal patient is one with light skin,
but dark hair. Prior to treatment with IPL, the involved area should be
shaved but other methods of hair removal should be avoided because some
remaining hair follicle is required for absorption of the light energy.
It is preferable to avoid direct sun exposure for about one month prior
to treatment because sun exposure would increase the melanin content of
the skin and therefore increase the possibility of skin injury while reducing
the effectiveness of hair removal. The proper eye protectors must be worn
both by the patient and the operator of the IPL device in order to avoid
damage to the retina of the eye.
IPL therapy is usually not painful at all, however for some and depending
on the location, some mild discomfort can be felt. At its worst the discomfort
could be equated to the feeling of a tiny elastic band being flicked against
the skin.
Some hair is immediately vaporized at the time of the procedure, but most
often the hair falls out over the course of the next week. Frequently,
there will be some very mild swelling of the skin, a slight redness or
itchiness which feels like a light sunburn lasting only a few days. No
treatment is usually necessary and normal daily activity can resume immediately.
Avoidance of direct sunlight is recommended for the next six weeks.
In summary, the use of Intense Pulsed Light is a highly effective, safe
and cost effective method that surpasses all other treatments available
today for the removal of unwanted hair.
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