Laser Hair Reduction (LHR) is one of the most in-demand clinical aesthetic procedures globally. Modern diode, Nd:YAG, and Alexandrite lasers offer versatile platforms. However, laser therapists must understand how to customize treatment parameters to achieve follicular destruction without causing epidermal burns.
1. Fluence (Energy Density)
Fluence measures the delivered energy in Joules per square centimeter (J/cm²). The goal is to heat the hair follicle to approximately 70°C to damage the stem cells. Darker Fitzpatrick skin types require lower fluences to prevent competitive absorption by epidermal melanin.
2. Pulse Duration (Pulse Width)
Pulse duration refers to the time the laser beam remains in contact with the skin. It must be balanced against the Thermal Relaxation Time (TRT) of the target. For thick, coarse hair, longer pulse durations are safer, while fine hair responds better to shorter pulse widths.
3. Spot Size Selection
Larger spot sizes (e.g., 15mm to 18mm) allow for deeper light penetration due to decreased scattering. They also speed up the procedure for large anatomical areas like the back and legs. Use smaller spot sizes (e.g., 6mm to 8mm) for targeted areas like the upper lip.
Frequently Asked Questions
Darker skin contains more melanin, which absorbs laser energy. Lowering the fluence prevents the epidermis from absorbing excessive heat, thereby avoiding burns and hyperpigmentation.
Larger spot sizes reduce light scattering in the tissue, allowing the laser energy to penetrate deeper into the hair bulb. They also shorten treatment times for large areas.
Most clients require 6 to 8 sessions spaced 4 to 8 weeks apart. This is because lasers can only target hair follicles in the active growth phase (anagen).
Yes, burns can occur if the fluence is set too high for the skin type, if the cooling system is not working, or if the practitioner overlaps pulses too closely.
Active cooling (contact cooling, cryogen spray, or chilled air) cools the skin surface immediately before and after the laser pulse to protect the epidermis from heat damage.
Fine hair contains less melanin, making it harder to heat. It requires shorter pulse durations and high fluences, which must be adjusted carefully to protect the skin.
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