CLS Laser Hair Removal Techniques 1

Question 1

Which principle underlies the effectiveness of laser hair removal?

Accepted Answer

Selective photothermolysis targeting melanin in the hair follicle

Answer

Selective photothermolysis uses a wavelength selectively absorbed by the target chromophore (melanin in the hair shaft and follicle), a pulse duration shorter than or equal to the thermal relaxation time of the follicle, and sufficient fluence to thermally destroy the follicle while sparing surrounding tissue.

Question 2

Why is laser hair removal generally less effective in patients with light blonde, red, or white hair?

Accepted Answer

Light hair has minimal melanin, the target chromophore, resulting in insufficient light absorption

Answer

Melanin is the primary chromophore targeted in laser hair removal. Blonde, red, and white hairs contain little to no eumelanin, so they do not absorb sufficient laser energy to generate the heat needed to thermally damage the follicle matrix and bulge. These hair colors are poor candidates for conventional laser hair removal.

Question 3

Which laser wavelength is most appropriate for hair removal in patients with Fitzpatrick skin types V–VI to minimize epidermal melanin damage?

Accepted Answer

1064 nm (Nd:YAG)

Answer

The 1064 nm Nd:YAG laser is preferred for dark skin types because melanin absorption is relatively low at this wavelength compared to shorter wavelengths. This allows the beam to penetrate deeper with less epidermal absorption, reducing the risk of epidermal burns and post-inflammatory hyperpigmentation in highly pigmented skin.

Question 4

What is the approximate thermal relaxation time (TRT) of a terminal hair follicle, which guides selection of appropriate pulse duration?

Accepted Answer

10–100 milliseconds

Answer

The thermal relaxation time of a terminal hair follicle is approximately 10–100 milliseconds, depending on follicle diameter. Laser pulse durations within this range allow selective heating of the follicle. Pulses longer than the TRT allow heat to diffuse to surrounding tissue, increasing side effects; shorter pulses may be subtherapeutic.

Question 5

During a laser hair removal session, a patient with a tan reports sunbathing two days prior. What is the most appropriate course of action?

Accepted Answer

Postpone treatment until the tan fades (typically 4–6 weeks), then reassess and adjust parameters

Answer

A recent tan significantly increases epidermal melanin, reducing the contrast between skin and hair follicle and increasing the risk of epidermal burns, blistering, and post-inflammatory hyperpigmentation. Treatment should be postponed until the tan has fully faded and the patient's baseline skin type is used for parameter selection.

CLS - Certified Laser Specialist Practice Test

CLS - Certified Laser Specialist Practice Test

CLS Laser Hair Removal Techniques 1