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.
