CLS Study Guide 2026
Everything you need to pass the CLS exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CLS Exam Format at a Glance
📚 CLS Topics to Study (45)
✍️ Sample CLS Questions & Answers
1. Which laser is considered the gold standard for treating port wine stains?
The pulsed dye laser is the gold standard for port wine stains because its wavelength selectively targets oxyhemoglobin with minimal epidermal collateral damage.
2. What is internal validity in a laser clinical study?
Internal validity refers to how well a study is designed to rule out alternative explanations for observed effects, allowing causal inferences within the study sample. Threats to internal validity include selection bias, confounding, and measurement error.
3. What should be done immediately after laser treatment?
Immediately after laser treatment, applying a cold compress helps to reduce post-treatment discomfort, swelling, and erythema (redness). The cooling effect constricts blood vessels and helps dissipate any residual heat in the treated area. This action minimizes inflammation and promotes a more comfortable and faster recovery for the patient.
4. How should a CLS manage a client who develops hypopigmentation (loss of skin color) following laser treatment?
Hypopigmentation should be documented and the client referred to a physician for evaluation, as it may indicate permanent melanocyte damage requiring specialist management.
5. Solar lentigines (age spots) and café-au-lait macules are treated with Q-switched lasers. What parameter distinguishes successful treatment of solar lentigines from incomplete response?
When treating solar lentigines, the target is selective photothermolysis of melanin within the pigmented lesion. Correct treatment produces frosting or immediate lightening that is confined to the pigmented spot, sparing the surrounding normally pigmented skin. Frosting extending into surrounding skin indicates too much energy and risk of hypopigmentation in uninvolved areas.
6. What is the ideal skin type for laser hair removal with Alexandrite lasers?
Alexandrite lasers, with a wavelength of 755 nm, are highly absorbed by melanin, making them very effective for hair removal in individuals with lighter skin types (Fitzpatrick I-III) and dark hair. Using an Alexandrite laser on darker skin types (Fitzpatrick IV-VI) carries a higher risk of epidermal damage and pigmentary changes due to increased melanin absorption in the skin itself, rather than just the hair follicle.