Red Light Therapy for Chronic Pain: Scientific Evidence

In 2023, a literature review analyzed 11 randomized controlled trials to evaluate the effects of photobiomodulation therapy (PBMT) on chronic pain and inflammation across conditions including knee joint pain, lower back pain, fibromyalgia, jaw pain, tooth and gum pain, and post-surgery pain. The selected trials used wavelengths ranging from 780 nm to 1,064 nm, with fluence levels of 8 to 133 J/cm2, and were drawn from an initial search of 96,751 articles across 5 databases covering studies published between 2017 and 2022. Of the 11 trials, 5 found that PBMT positively influenced chronic pain, 1 found benefit only in the short term, 2 found marked improvements in inflammation, and 1 found no improvement in chronic pain while another found no improvement in inflammation. The review described PBMT as a safe and non-invasive treatment approach, while also noting that more research is needed to clarify its effects, particularly in the long term.

Pain intensity fell by 65.2% after treatment and by 58.6% at a 15 day follow-up in a 2022 randomized controlled trial testing laser ear acupuncture (laser auriculotherapy) against no treatment in 47 patients with chronic spinal pain. The 24 patients in the experimental group received 10 sessions of laser ear acupuncture at 808 nm, 100 mW, and 4 J per point applied to ear acupuncture points for 40 seconds, twice a week over 35 days, while the 23 patients in the control group received no intervention. Compared to the control group, experimental group patients showed significantly greater reductions in pain intensity and improvements in sensitivity to pain, with those differences still present at the 15 day follow-up. Results were assessed at 3 time points: before treatment, immediately after the final session, and 15 days later.

Across 8,889 patients treated at a single pain clinic in Japan, a 2012 observational study examined the effects of low level laser therapy (LLLT) delivered via the proximal priority laser technique (PPLT), in which laser was applied to the neck to create a whole body effect. Treatment used a GaAlAs diode laser at 830 nm, 60 mW, and 1,200 mW/cm2 in contact mode against the neck skin, combined with gentle neck and trunk stretching, over a 56 day period. Blood flow imaging tools showed increased blood flow to the brain and through the neck arteries following PPLT sessions, with a whole body warming effect that grew stronger with each subsequent session. The study reported that PPLT may help reduce chronic pain, with the warming effect appearing within hours to days of treatment.

Whether adding linear-polarized near-infrared light irradiation (LPNIR) to nerve or local block therapy could improve pain outcomes was the central question of a 2012 randomized controlled trial in China involving 52 patients with shoulder joint pain, back muscle pain, or elbow pain. 36 females and 16 males aged 19 to 79 years were split into 2 groups, with Group I receiving LPNIR at 830 nm and 1.8 W for 10 minutes alongside their block therapy, and Group II receiving block therapy alone, both treated 3 times per week over 3 weeks. Immediately after treatment, Group I showed significantly greater pain reduction than Group II, though by the 6 month follow-up no meaningful difference between the groups remained. Across both groups, no side effects were observed in any patient.

3 types of phototherapy devices for chronic pain were compared in a 2009 observational study, including low-level laser therapy (LLLT), linearly polarized near-infrared light treatment, and xenon light treatment, all operating across a wavelength range of 780 to 1,400 nm. The study described available LLLT devices as using semiconductor lasers with a mean power of around 1 W, while a newer device offered a peak power of 10 W at the same 1 W mean output. All 3 modalities showed significant pain relief effects in double blind tests, and the higher-powered 10 W LLLT device was found to be no less safe than the standard 1 W version while reaching around twice the treatment depth.