Light and photobiomodulation
Low-level laser/light therapy (LLLT)
LLLT is the older name for photobiomodulation: light at intensities too low to heat tissue, applied to produce a biological effect. The name has been formally superseded because "low-level" was never defined and the effect is not limited to lasers.
Also called LLLT, low-level laser therapy, cold laser, soft laser
Where the name came from. LLLT arose in the 1960s and 70s around low-power lasers, and was sometimes marketed as “cold laser” or “soft laser” to distinguish it from surgical lasers that cut or coagulate.
Why it was retired. Anders, Lanzafame and Arany argued in Photomedicine and Laser Surgery (2015) that the term should be replaced by photobiomodulation, on three grounds: “low-level” has no numerical definition, so it cannot be specified or reproduced; LEDs produce the same effects as lasers, so “laser” is misleading; and light can suppress as well as enhance a cellular activity, so “modulation” is more accurate than the implied stimulation. Photobiomodulation is now the preferred indexing term.
Why it still matters. Decades of literature is indexed under LLLT, so a search for photobiomodulation alone will miss a large part of the research. Several studies on our own studies pages use the older term.
One thing the old name got right. Both terms describe non-thermal light. If a device is warming you, the heat comes from something else — in our saunas, the far infrared and the steam — and is separate from photobiomodulation.
Why it matters here
A large share of the research you will come across uses this older name rather than photobiomodulation. Knowing the two describe the same thing keeps you from missing evidence, or from counting the same study twice.