DHA Laser Hair Reduction exam questions

6 worked Laser Hair Reduction practice questions

Original exam-style questions from the bank, spread across the blueprint domains. They are not real or recalled exam questions. Try each one, then open the answer for the rationale and reference. None of them appear in the free mock exam, so reading them will not spoil it.

1. Question 1 · Client Assessment and Contraindications

   During consultation, a client mentions she started oral doxycycline last week for acne. What is the most appropriate action?

   1. ATreat as normal
   2. BTreat with higher fluence
   3. CAsk her to stop the antibiotic
   4. DDefer treatment and seek medical advice
   Show answer and explanation

   Correct answer: D. Defer treatment and seek medical advice

   Doxycycline is photosensitising, so treatment should be deferred and the supervising doctor consulted about timing. The technician should not advise stopping a prescribed medicine.

   Reference: Goldberg DJ. Laser and Light, Procedures in Cosmetic Dermatology, 4th ed.

2. Question 2 · Infection Control, Consent and Ethics

   During consent, how should the expected outcome of laser hair treatment be described?

   1. ALong-term reduction; maintenance may be needed
   2. BPermanent, complete removal of all hair
   3. CFull results after one session for all hair
   4. DGuaranteed removal of white and grey hair
   Show answer and explanation

   Correct answer: A. Long-term reduction; maintenance may be needed

   Lasers produce long-term hair reduction rather than complete permanent removal, and occasional maintenance sessions may be needed. Promising complete removal or guaranteed results is misleading and undermines valid consent.

   Reference: Gan SD, Graber EM. Dermatol Surg 2013 (Laser hair removal: a review)

3. Question 3 · Laser Physics and Light-Tissue Interaction

   In laser hair reduction, which chromophore in the hair follicle absorbs the light energy?

   1. AHaemoglobin
   2. BWater
   3. CMelanin
   4. DCollagen
   Show answer and explanation

   Correct answer: C. Melanin

   Laser hair reduction relies on melanin in the hair shaft and follicle absorbing the light and converting it to heat that damages the follicle. Haemoglobin is the target for vascular lasers, and water for ablative lasers.

   Reference: Anderson RR, Parrish JA. Science 1983 (selective photothermolysis)

4. Question 4 · Complications and Their Management

   After several sessions on the lower face and neck, a Fitzpatrick type IV client notices increased dark hair growth around the treated area. What is the most likely explanation?

   1. AParadoxical hypertrichosis
   2. BNormal regrowth of telogen hairs
   3. CFolliculitis
   4. DAn allergic reaction to gel
   Show answer and explanation

   Correct answer: A. Paradoxical hypertrichosis

   Paradoxical hypertrichosis is new or thicker hair growth in or around treated areas, most often on the face and neck in darker skin types and possibly related to subtherapeutic heating. Normal telogen regrowth does not increase hair density beyond baseline.

   Reference: Lim SP, Lanigan SW. Lasers Med Sci 2006 (adverse effects of laser hair removal)

5. Question 5 · Laser Physics and Light-Tissue Interaction

   With the same fluence, how does increasing the spot size affect light delivery to the hair bulb?

   1. AIt increases depth because less light is lost to scatter at the edges
   2. BIt reduces depth because energy spreads over a wider area
   3. CIt has no effect on depth of penetration
   4. DIt shortens the pulse duration automatically
   Show answer and explanation

   Correct answer: A. It increases depth because less light is lost to scatter at the edges

   Larger spots lose proportionally less light to lateral scatter, so more energy reaches deeper structures such as the hair bulb at the same fluence. Small spots lose much of their energy to scatter and penetrate less deeply.

   Reference: Goldberg DJ. Laser and Light, Procedures in Cosmetic Dermatology, 4th ed.

6. Question 6 · Laser Physics and Light-Tissue Interaction

   A laser delivers 15 J per pulse through a 10 mm diameter circular spot. What is the approximate fluence?

   1. A1.5 J/cm2
   2. B4.8 J/cm2
   3. C19 J/cm2
   4. D150 J/cm2
   Show answer and explanation

   Correct answer: C. 19 J/cm2

   Spot area = pi x (0.5 cm)^2 = 0.785 cm2, and 15 J / 0.785 cm2 = about 19 J/cm2. Using the diameter instead of the radius in the area calculation gives about 4.8 J/cm2, a fourfold underestimate.

   Reference: Goldberg DJ. Laser and Light, Procedures in Cosmetic Dermatology, 4th ed.