What are the available wavelengths for LHR?

• A. 400-700 nm
• B. 600-1100 nm
• C. 10-200 nm
• D. 1200-1800 nm

Answer: (B)

Laser hair removal works best when the wavelength can reach the hair follicle and be absorbed by follicle melanin while sparing surrounding skin. The near-infrared window, roughly 600 to 1100 nanometers, provides that balance: it penetrates enough to reach the follicle and is still absorbed by melanin, enabling effective treatment with manageable risk to the epidermis. That’s why common LHR devices use wavelengths around 755 nm, 810 nm, and 1064 nm—all inside the 600–1100 nm range. Wavelengths shorter than 600 nm are absorbed too strongly by epidermal pigment, increasing the risk of surface damage, while wavelengths longer than about 1100 nm are less efficient at reaching the follicle due to higher water absorption and scattering, reducing efficacy.