| Blue-light wavelength | Check the stated wavelength in nanometres (nm), not just a “blue light” label. | Consumer devices commonly specify blue light around 405–420 nm. | Blue light is used in some acne-focused light devices. Wavelength alone does not establish effectiveness; intended use, treatment schedule, and device testing also matter. |
| Red-light wavelength | Look for a precise wavelength or range and confirm that it is listed for the device’s red LEDs. | Commonly specified red-light bands include approximately 630–660 nm. | Red light is commonly used in devices marketed for skin appearance. Results depend on the device and protocol; avoid treating a wavelength claim as a guaranteed outcome. |
| Near-infrared (NIR) | Check whether NIR is included and whether its wavelength is stated separately from visible red light. | Consumer devices may specify NIR around 810–850 nm. NIR is not visible to the eye. | NIR may be included alongside red LEDs, but a mask’s NIR output and coverage can differ from its visible-light output. Verify the device’s specifications for each band. |
| Single-band or combination light | Compare the actual wavelengths provided with your intended use; check whether bands operate together or in separate modes. | Some masks offer red only; others combine red with blue and/or NIR. | More wavelengths do not automatically mean better performance. A simpler device may be easier to match to a specific routine, while multiple modes can offer flexibility. |
| Face coverage and fit | Check coverage around the forehead, cheeks, nose, chin, and jawline, plus whether the mask sits evenly on your face. | Look for clear product images or diagrams showing the illuminated area and any unlit gaps. | Fit affects how consistently light reaches different areas. A mask that leaves gaps or sits far from the skin may deliver uneven exposure. |
| LED layout and distance | Look for a layout diagram and information on the distance between LEDs and skin during use. | LED count by itself is not a reliable measure of light reaching the skin. | Output depends on more than the number of LEDs, including their power, optics, spacing, and distance from the treatment area. |
| Irradiance at the skin | Prefer a stated irradiance in mW/cm² measured at the treatment surface, with the measurement distance specified. | There is no single universally applicable irradiance value that establishes a mask as effective for every purpose. | Power ratings in watts or LED counts do not tell you how much light reaches your skin. Compare irradiance only when measurement conditions are clearly stated. |
| Session dose and treatment time | Check the recommended session length, frequency, and any dose information in J/cm². | When irradiance and exposure time are known, radiant exposure can be calculated: J/cm² = W/cm² × seconds. | Shorter sessions do not necessarily mean a stronger or more effective treatment. Follow the device instructions rather than increasing exposure on your own. |
| Eye comfort and safety | Review eye-safety instructions, light-shielding design, and any precautions for photosensitivity or light-sensitive medication. | Visible blue light can be bright; NIR may be invisible even when it is on. | Do not look directly at LEDs. Follow the manufacturer’s directions and seek medical advice if you have a relevant eye condition, photosensitivity, or medication-related concern. |
| Evidence and documentation | Look for wavelength, irradiance, measurement method, intended use, and clear instructions—not just broad performance claims. | Specifications should identify the tested output and the conditions under which it was measured. | Transparent, testable specifications make it easier to compare devices. Regulatory clearance, where applicable, is specific to the product and its stated use. |