Low-level Light Therapy
In 2007, low-level light therapy (LLLT) was approved by the FDA as a treatment for hair loss. LLLT is also known as low level laser therapy, red light therapy, cold laser, soft laser, biostimulation, and photobiomodulation.[24–26] Most experts agree that LLLT is safe for the treatment of hair loss, but more studies are needed to confirm its therapeutic effects. LLLT was discovered in the 1960s and first used by the National Aeronautics and Space Administration (NASA) to accelerate wound healing in space. Since then, LLLT has been used to reduce neurogenic pain, reduce inflammation, and promote wound healing.[25–27] Other uses include nonmelanoma skin cancer and its precursors, acne vulgaris, photorejuvenation, hidradenitis suppurativa, and psoriasis. It may also prove helpful in killing bacteria, fungi, and viruses. LLLT has also been used to achieve attenuation of retinal toxicity in methanol-poisoned rats. The role of LLLT in hair growth was discovered accidentally in 1967. In an attempt to test if LLLT causes cancer in shaved mice, researchers discovered that these mice did not develop cancer, but instead grew hair.
Before describing the mechanisms of LLLT, a brief discourse into its terminology will be taken. The term "laser" refers to the fact that monochromatic light is used. This is in contrast to light emitting diode (LED). The term "low level" alludes to the fact there is a specific wavelength of light that has optimal therapeutic effects, and any level higher or lower than this may not be proficient. This therapeutic window ranges roughly from 600 to less than 1,400 nm, and is close to the absorption spectrum of hemoglobin and water, respectively. Furthermore, respiratory chain components (mainly cytochrome c) have a similar absorption spectrum. This low level results in a negligible change in tissue temperature.
South Med J. 2010;103(9):917-921. © 2010 Lippincott Williams & Wilkins