Flashcards in Laser hair removal Deck (159):
The three anatomical units of the hair follicle are the infundibulum, isthmus and inferior segment
The infundibulum is the region from the hair follicle orifice to the arrector pili muscle.
F Hair follicle orifice to sebaceous duct entrance.
The isthmus is the region between the entrance of the sebaceous duct and the arrector pili muscle.
The inferior segment extends from the insertion of the arrector pili muscle to the base of the follicle, including the hair bulb.
The hair bulb is composed of matrix cells only.
F Interspersed melanocytes also.
The matrix cells of the hair bulb form the outer root sheath, the inner root sheath and the hair shaft itself.
The inner root sheath (from the outside inward) consists of three layers: cuticle, Huxley and Henle.
F From outside inward -- Henle, Huxley and cuticle.
The three layers of the hair shaft (from the outside inward) are: cuticle of the hair shaft, cortex and medulla.
The lowermost aspect of the permanent part of the hair follicle is at the level of the insertion of the arrector pili muscle (the follicular bulge)
The anagen phase of the hair growth cycle refers to the transition period in which the bulbar part of the hair follicle, including matrical melanocytes, is almost totally degraded through apoptosis.
F This is the catagen phase.
The anagen phase refers to periods of active growth, where the rapidly developing bulbar matrix cells differentiate into the hair shaft and inner root sheath.
Anagen bulbs are 12-17mm below the skin surface.
Telogen refers to a resting phase in the hair growth cycle.
During telogen, the follicle decreases to approximately one-third of its former length, with the lowermost part coming to lie at the level of attachment of the dermal papilla.
F This occurs during catagen.
With new hair regrowth in early anagen, new epithelial cell division occurs near the arrector pili insertion, a new matrix develops, and hair growth resumes.
A population of stem cells capable of regenerating the follicle is within or near the hair bulb matrix.
There is a population of slow-cycling stem cells in the follicular bulge that arise off the outer root sheath at the site of the arrector pili muscle attachment, approx 1mm below the skin surface
Body sites with long hair (eg. scalp) have a prolonged telogen phase.
F Prolonged anagen phase.
Body sites with short hair (eg. female upper lip) have a short anagen phase.
T And prolonged telogen phase.
Duration of anagen growth of the upper lip is typically 16 weeks, catagen 1 week, and telogen 6 weeks.
The duration of anagen growth on the scalp is generally 150 weeks, catagen 1-3 weeks, and telogen 12 weeks.
There is no seasonal variation in hair growth in humans.
F Higher rate of growth in summer.
Variability in hair growth rates correlates with fluctuations in androgen levels.
There are two main types of hair: vellus and terminal.
F Three – also lanugo.
Hair diameter is determined by the size of the papilla and hair bulb.
Lanugo hairs are non-pigmented.
F Vellus hairs are non-pigmented.
Lanugo hairs are soft, fine hairs that cover a foetus. They are shed before or shortly after birth.
Secondary vellus hairs don’t have the same diameter as vellus hairs.
F They do.
Secondary vellus hairs represent miniaturised or hypoplastic lanugo hairs.
F Miniaturised or hypoplastic terminal hairs.
Secondary vellus hairs are non-pigmented.
F They are pigmented.
Both vellus and terminal hairs go through all stages of follicular growth, but the duration of anagen is much shorter for vellus hairs.
Vellus hairs are replaced by terminal hairs at puberty.
Terminal hairs are converted to secondary vellus hairs with androgenetic alopecia.
Vellus hair bulbs may extend 2-7mm into skin.
F Less than 1mm into skin.
Telogen hair bulbs may extend 10mm into skin.
F 2-7mm into skin.
The hair bulge maintains a constant depth throughout the hair cycle.
Follicular melanocytes produce two types of melanin – eumelanin (brown-black pigment) and pheomelanin (red pigment).
Melanocytes occur in the hair papilla/matrix.
F In the upper part of the hair bulb and outer root sheath of the infundibulum.
The ratio of melanocytes to keratinocytes in hair is 1:5.
Melanogenesis is halted during anagen and reinitiated during early catagen.
F Halted during catagen, reinitiated during early anagen.
Pigment transfer is halted during catagen, resulting in an unpigmented hair bulb.
F Halted during telogen – results in unpigmented telogen bulb.
Pheomelanin absorption is 30 times lower than eumelanin at 694nm and is poorly absorbed at wavelengths longer than 700nm
Brown and black hair contains ellipsoidal heavily melanised eumelanosomes.
Red hair contains incompletely melanised melanosomes or fewer melanosomes.
F This is true of blonde hair.
Red hair contains spherical pheomelanosomes.
Grey hair-producing follicles contain few melanocytes, with poorly melanised melanosomes.
White hair-producing follicles contain no dopa-positive melanocytes.
Tweezing and waxing can cause post-inflammatory hyperpigmentation, ingrown hairs, folliculitis and scarring.
Chemical depilatories provide permanent hair removal by destroying the entire hair shaft below the skin surface.
F Temporary hair removal by dissolving hairs by disruption of disulphide bonds.
Antiandrogenic medications can provide permanent hair loss.
F Only partial and temporary hair loss.
Vaniqa is 5% eflornithine hydrochloride cream.
Vaniqa acts as an irreversible inhibitor of ornithine decarboxylase, an enzyme that is critical for the biosynthesis of cationic polyamines which are necessary for cell growth.
Ornithine decarboxylase is expressed in the proliferating bulb cells of anagen hair follicles.
Vaniqa should be applied once every 2nd day.
F Twice daily.
temporary hair loss - grows back when stop using
The side effects of Vaniqa are minimal.
F Stinging, burning, acne, folliculitis.
Electrolysis can be used to destroy the hair follicle.
Electrolysis has an efficacy of 70-80% for destroying individual hair follicles.
Electrolysis can result in post-inflammatory hypopigmentation, hyperpigmentation and ice-pick scarring.
Laser hair removal is advocated in pregnant women.
F Best avoided, although no evidence it harms the foetus.
A past history of HSV at or near the laser treatment site requires prophylactic antiviral therapy.
A history of keloids or hypertrophic scar formation may preclude the use of lasers for hair removal.
Laser treatment should be avoided in patients taking photosensitising medications.
Laser treatment can be used safely within 1 month of cessation of isotretinoin.
F 6 months.
Past or current use of gold therapy is not a significant factor in the use of laser treatment.
F Laser should be avoided in such patients.
Lasers can be safely used in patients with psoriasis.
F Should avoid due to koebnerisation in psoriasis and other koebnerising skin diseases
The ideal candidate for laser hair removal is fair-skinned with dark terminal hair.
Patients with darker skin and dark hair are less ideal laser candidates.
Patients with blonde, gray, red or white hair are likely to have permanent hair removal with laser treatment.
Patients with skin types I and II have an increased risk for laser side effects.
F Skin types V and VI.
If an active tan is present, or there is recent sun exposure, laser treatment should be postponed up to 6 weeks to allow the tan to lighten to minimise potential side effects.
Patients should avoid excessive sun exposure for a month before and during the entire laser treatment course.
After multiple laser treatments, the treatment areas will have less hair growth, although hair thickness remains the same.
F Hair growth is finer.
Long-term hair reduction is strongly correlated with hair colour, skin colour and tolerated fluence.
With the use of higher fluences, as are needed for Fitzpatrick skin types III or greater, the percentage hair loss is increased, and complete permanent hair removal is more likely.
F Lower fluences are needed – hair loss is decreased, complete permanent hair removal less likely.
Laser treatment risks for all patients include blistering, ulceration, scar formation, folliculitis or acne flare, hyperpigmentation, hypopigmentation, increased hair growth, poor-to-no response, and recurrence.
Bleaching creams should be avoided in patients with Fitzpatrick skin types III or greater and for patients with recent sun exposure prior to laser treatments.
F These can be used.
Plucking, waxing and electrolysis are to be avoided prior to laser treatments so that the hair shaft remains intact.
Shaving, bleaching and depilatory creams may be used prior to laser.
Laser hair removal is based on the principle of selective photothermolysis – confining thermal injury to the targeted chromophore.
PDT is not a viable means of inducing temporary hair loss.
F Can induce loss for 3 months.
The hair bulge and bulb are important for permanent hair follicle destruction.
Catagen hair bulbs are unpigmented and thus not active targets for light absorption during laser treatment.
F Telogen hair bulbs.
Follicles in early catagen are more response to laser and light treatment.
F Early anagen.
The optical window for targeting melanin with lasers is between 300 and 590nm.
F 600 and 1100nm.
Using longer wavelengths of light (800nm or greater) allows deeper penetration into the skin.
At longer wavelengths, shorter fluences are required for follicular destructions.
F Higher fluences due to decreased melanin absorption.
The optima wavelength for hair removal is dependent on the colour contrast between the epidermis and hair shaft.
Individuals with light skin and dark hair can tolerate all wavelengths of light with minimal risk of epidermal damage.
Red and red-brown hairs require longer wavelengths.
Blond, white and gray hairs require the shortest wavelength possible to allow for maximum melanin absorption.
Q-switched lasers produce instantaneous hair shaft vaporisation and a photoacoustic effect through the delivery of very short pulses.
The optimal pulse duration for permanent hair reduction while minimising epidermal injury is between 50 and 100 ms.
F 10 and 50ms.
Longer pulse widths allow for higher tolerated fluences for all skin types.
The delay between chromophore heating and distant target heating is referred to as thermal relaxation time.
F Thermal damage time.
Thermal damage time is the time required to irreversibly damage the target with sparing of the surrounding tissue.
With laser hair removal, the chromophore is melanin within the hair follicle, whereas the ultimate target is the follicular stem cell which is located at the same site.
F Follicular stem cell located at the bulb or bulge.
The time required to transfer heat from the hair follicle to the bulb or bulge is referred to as the thermal damage time.
Optical scattering by dermal elastin causes light to diffuse as it penetrated into the dermis.
Dermal collagen (not elastin).
Smaller spot size (under 9mm) allows for a greater likelihood that photons will be scattered back into the incident collimated beam with resultant beam broadening
This is true for larger spot size (over 9mm)
therefore a smaller spot size (greater photon density) results in deeper energy penetration
For even large spot sizes, there are edge effects, with areas near the edge of the beam receiving less fluence. Slight overlapping of treatment pulses helps to reduce this occurrence.
Higher fluences can be used very safely in darker-skinned patients.
F Higher fluences will cause injury to overlying skin.
Selective epidermal cooling is employed with lasers to reduce injury to the overlying skin.
Types of cooling systems employed in conjunction with laser hair removal include: passive cooling with aqueous gel.
Types of cooling systems employed in conjunction with laser hair removal include: active contact cooling with water encased in a plastic housing.
F Encased in a glass or sapphire housing.
Types of cooling systems employed in conjunction with laser hair removal include: dynamic active cooling with a cryogen spray.
Types of cooling systems employed in conjunction with laser hair removal include: forced air cooling.
Evaporative cooling systems typically employ a cryogen spray delivered after the laser pulse.
F Before the laser pulse.
The epidermal protection afforded by the use of surface cooling allows for increased tolerated fluences for all skin types.
Histologically, laser hair removal results in reduction in the number of terminal hairs and an increase in vellus-like hairs without fibrosis.
Ruby laser uses of wavelength of 700nm.
Ruby laser has significant dose-related side effects compared to other laser systems.
The use of ruby laser is acceptable in patients with a history of persistent post-inflammatory hyperpigmentation, darkly tanned skin, or a skin type darker than Fitzpatrick type III.
F Should be avoided in these patients.
Long-pulsed alexandrite lasers (755nm) can be used for laser hair removal.
Alexandrite lasers have a longer wavelength which allows a slightly greater depth of penetrations.
Diode lasers are wavelength 700-710nm.
Advantages of diode lasers include longer pulse durations and longer wavelengths, allowing for treatment of Fitzpatrick skin type III and IV patients because there is less epidermal melanin absorption.
Long-pulsed Nd:YAG is less effective in treating patients with lighter hair.
but safe treatment option for patients with Fitzpatrick skin types III–V
Nd:YAG laser has a wavelength of 1064nm-
Reduced melanin absorption of the Nd:YAG requires the use of higher fluences for adequate follicle injury.
YAG laser is not a safe treatment option for patients with Fitzpatrick skin types III-V-
Q-switched Nd:YAG lasers are available for hair removal.
YAG systems don’t produce long-term hair removal-
IPL uses non-coherent, multiwavelength light for hair removal.
The output spectrum of IPL extends across the 400-1200nm range.
F 500-1000nm range.
Filters are used in IPL to allow more selective treatment.
A disadvantage of the IPL system is that most devices use large circular spots, creating difficulty is treating convex or concave hair bearing areas.
F Large rectangular spots.
Microwave-based hair removal systems can be used for hair removal in all body sites.
F Not the face.
Oral antiviral medications is initiated 24hours before laser procedures and continued for a total of 7 days in patients with a history of HSV near the laser treatment site.
Topical anaesthetic should not be used prior to hair removal laser.
Patients should not clip or shave the treatment site before laser hair removal.
F Should cut hair to 1mm to minimise plume and prevent hair char/epidermal damage.
Make-up doesn’t need to be removed prior to laser hair removal.
All staff and the patient must wear protective glasses or goggles with a minimum optical density of 5 specific for the wavelength of light being used.
The plume generated by vaporised hair shafts has a sulphur smell, which in large quantities can be irritating to the respiratory tract.
The lowest possible fluence and smallest spot size should be used to obtain best laser hair removal results.
F Highest tolerated fluence and largest spot size.
Traction of the skin should be avoided during laser hair removal treatments.
F This decreases the relative depth of the bulb and bulge relative to the skin surface.
If any whitening, vesiculation or forced epidermal separation (positive Nikolsky’s sign) are noted after laser treatment, the fluence must be decreased.
Treatment sites bearing tattoos can be treated for laser hair removal without any risk to the patient.
F Risk of altering tattoo pigment.
Individuals with red, gray or white hair may lack sufficient follicular melanin to allow permanent hair reduction
Individuals with darker skin present with an increased risk of side effects at any given energy, although shorter wavelengths offer some degree of protection of epidermal melanin
Darker-skinned patients benefit from longer pulse durations (>30ms) because this allows for the simultaneous cooling of the band of melanin at the DEJ, and more time for heat extraction from the skin surface, thus reducing epidermal injury.
T = Fitzpatrick skin types III and IV
A laser test spot should be considered for any patient in whom there is concern about the potential for side effects.
There are no additional risks associated with the treatment of vellus (compared to terminal) hairs, in particular those of the jawline.
F New hair growth may be induced as a result of sublethal laser doses, with resultant induction of terminal hair.
Paradoxical increased growth of terminal hair after laser treatment is more common in Caucasian females.
F Females of Meditteranean descent.
For highly dense hair-bearing areas (eg. back, chest), lower fluences should be used to prevent non-selective damage through excessive heat diffusion.
Laser-treated sites generally demonstrate perifollicular oedema and erythema, both lasting up to 48 hours.
F Erythema may persist up to 1 week.
Perifollicular crusting lasting 7-10 days is an expected side effect of laser hair removal treatment.
F This occurs infrequently.
If erythema lasts beyond 2 days than a low to mid potency corticosteroid cream may be applied twice a day until it subsides
F If lasts beyond 10 days
Purpura is rarely observed post laser hair removal – it resolves over 2 weeks when noted.
Treated hair will continue to ‘grow’ for 1-2 weeks after laser hair removal treatment, until each hair is expelled from the skin surface.
Patients should be advised not to shave, tweeze, or wax treated hairs to expedite their removal once inflammation has resolved after laser treatment.
F They can do these things.
Depending on the treatment site, patients will note hair regrowth of those hairs not in anagen during treatment within 2-6 weeks thereafter.
Strict photoprotection is required for the duration of the laser hair removal treatment course.
Treatments are spaced every 12-16 weeks for the face, axillae and bikini areas.
F Every 6-8 weeks. Legs/chest/arms/back is every 12-16 weeks.
Pigmentary changes that occur as a complication of laser hair removal may take months to year for full resolution.
Temporary or permanent leukotrichia may follow laser hair removal therapy and IPL.
Hair colour restoration after laser-induced leukotrichia occurs more frequently in older patients.
F Younger patients – melanocytes less likely to be susceptible to thermal damage.
lasers with longer wavelengths are safer for treating darker skin types
because they penetrate more deeply so less risk of epidermal melanin damage
longer wavelength lasers need high fluences to effectively target melanin