Depth of penetration of an 850nm wavelength low level laser in human skin.
Level 5 - mechanism / opinion, no new human data
Ex vivo laboratory measurement on excised human tissue samples.
PubMed 18077939 · doi:10.3727/036012907815844165
What was done
Human abdominal skin samples up to 0.784 mm thick were harvested via dermatome following abdominoplasty procedures. The excised tissue samples were irradiated with a gallium aluminium arsenide laser (850 nm wavelength, 100 mW, 24 kHz, 0.28 mm probe diameter), and transmitted energy was measured directly using an external optical power meter.
What was found
Laser radiation intensity decreased by 66% after passing through a 0.784 mm sample of human abdominal tissue, with the majority of radiation absorbed within the first 1 mm of skin.
Why it matters
These direct tissue measurements provide an empirical estimate of near-infrared laser attenuation in human skin, contrasting with theoretical models that predict penetration depths up to 50 mm.
Limits
The abstract does not state the total number of donors or skin samples evaluated. Measurements were performed ex vivo on non-perfused abdominal skin, which may differ optically from living, vascularized tissue and other anatomical sites. Only a single wavelength, power setting, and maximum thickness (0.784 mm) were tested.
Cited by
- supports Long-wavelength light between approximately 620 nm and 850 nm from red light or near-infrared light devices penetrates deep into the skin.
- contradicts Long-wavelength red light passes all the way through the human body, even through light clothing, and is absorbed by the water in mitochondria to improve mitochondrial function in every cell with mitochondria.