Red Light Therapy for Burning Mouth Syndrome: Scientific Evidence

According to a 2025 systematic review and meta-analysis from Brazil, low level laser therapy compared favourably with placebo, no laser, clonazepam and alpha-lipoic acid for burning mouth syndrome (BMS). 13 randomized trials with 503 participants were included from 528 references, 7 reviewed descriptively and 6 pooled by laser colour, red or infrared, with pain, oral quality of life, adverse effects and anxiety and depression as the outcomes. Less pain was reported with the laser than with placebo or clonazepam, and quality of life was better, but the reviewers rated the certainty of the evidence as low and very low. The true effect may therefore differ substantially from the estimate, and the review called for better-conducted trials.

Researchers in Tunisia reviewed 9 clinical trials of low level laser therapy (LLLT) for primary burning mouth syndrome in a 2024 systematic review. Searches up to March 2023 produced 21 candidate articles, 12 of which were excluded on full reading, and the 9 retained used diode lasers from 685 to 830 nm at 1 mW to 4 W, plus 1 study using a 1064 nm laser, with 6 of the 9 rated at low risk of bias. 5 of the 9 trials reported a significant reduction in pain or burning compared with placebo, and in 2 of them the reduction was still present at 2 and 4 months. LLLT may be of benefit for the condition, though the wide spread of laser settings makes a clear recommendation difficult and standardised trials are needed.

Published in 2024, this clinical trial from Portugal followed patients with burning mouth syndrome (BMS) through 12 months of photobiomodulation with low level laser therapy in an outpatient setting. 15 people completed it, 14 women and 1 man, each receiving 660 nm light at 100 mW and 6 J/cm² for 1 minute in contact with the affected areas once every 2 weeks, with quality of life measured by a standard 5-part health questionnaire at the start and at 6 and 12 months. According to the study, 4 of the 5 parts of the questionnaire, self-care, usual activities, pain and discomfort, and anxiety and depression, improved significantly, along with how healthy patients felt. 13 of the 15 participants reported stopping or reducing their medication for the condition.

Researchers in China looked back at 94 patients with burning mouth syndrome treated with a single session of low level laser therapy (LLLT) in a 2024 retrospective study. Each patient received 635 nm light inside the mouth at 100 mW/cm² and 2 J/cm², with pain rated on a standard scale immediately before and after. The study found that 71.3% of patients reported an immediate decrease in pain, and the average score straight after the session was significantly lower than before it. Starting pain level, smoking or alcohol history, dry mouth and gum problems were the only baseline factors linked to how well it worked.

Researchers in 2024 tested laser therapy alone, medication alone, and the 2 combined for the pain of burning mouth syndrome in a randomized controlled trial in China. 45 patients were randomly split into 3 groups of 15, with the laser groups receiving 1064 nm light at 500 mW for 10 seconds per point, held 1 mm from the lining of the mouth, and pain rated on a standard 0 to 10 scale before and after treatment. All 3 groups showed a significant reduction in pain scores, and the differences between the groups were also statistically significant. The authors concluded that laser and medication each reduce oral burning pain, and that the combination produced the largest improvement.

Researchers in Brazil compared photobiomodulation (PBM) with transcutaneous electrical nerve stimulation (TENS) for burning mouth syndrome (BMS) in a 2023 randomized clinical trial. 25 patients were treated once a week for 8 weeks: 13 with 808 nm light at 100 mW, 3330 mW/cm², 6 J, and 200 J/cm² for 1 minute, and 12 with TENS, with pain, saliva flow, dry mouth, and taste changes assessed at the start, after the 4th and 8th sessions, and 30 days after treatment ended. Both treatments reduced pain significantly during and after the course, and the trial found a better response to PBM than to TENS between the end of treatment and the 30-day follow-up. Saliva flow rose in the TENS group, while neither group showed a clear change in dry mouth or taste.

A 2022 clinical trial in the United Kingdom evaluated photobiomodulation (PBM) against standard pain medication for nerve pain in the mouth, including burning mouth syndrome (BMS). 28 patients, 18 in the PBM group with an average age of 58 and 10 in the medication group with an average age of 56.8, most of them women and about 2 in 3 with BMS rather than nerve injury from dental treatment, were followed for 9 months, with the PBM group receiving 810 nm light at 200 mW, 1970 mW/cm² and 54 J for 30 seconds per point in near contact, in 10 treatments over 5 weeks. The trial found that worst pain in the PBM group fell by 3.67 points from a starting 7.61 on a 0 to 10 scale by the end of treatment and was still 3.47 points lower at 9 months, while the medication group's reductions ran from 1.4 to 2.3 points and several patients needed higher doses. No patient reported any adverse effect during the 10 treatments.

When reviewers in the United Kingdom sorted 22 randomized trials of burning mouth syndrome treatment into 9 categories in 2022 meta-analysis, laser therapy was 1 of 3 approaches that held up at both short-term and long-term follow-up. The trials, 403 participants in all, had compared a treatment against placebo or another option with at least 2 months of follow-up, and ranged across drugs, plant-based remedies, alpha-lipoic acid, low level laser therapy, saliva substitutes, transcranial magnetic stimulation and cognitive behaviour therapy. Cognitive behaviour therapy, capsaicin and clonazepam applied in the mouth, and laser therapy each showed a favourable outcome at 3 months and beyond, while plant-based remedies helped only in the short term. The authors concluded that larger trials across more centres, with more arms and longer follow-up, are needed before a standard treatment can be set.

4 treatment options, verbal and written information alone, B vitamin injections, probiotics for the mouth, and low level laser therapy (LLLT), were compared in a 2022 randomized clinical trial of burning mouth syndrome in Croatia. 62 newly diagnosed patients completed the study after random allocation to 1 of the 4 groups, with the laser group receiving 685 nm light at 30 mW and 2 J/cm², and quality of life related to oral health as the main measure alongside a 0 to 10 symptom scale. The trial found that only the probiotic and the LLLT groups showed a statistically significant improvement in quality of life, with the largest effect in the probiotic group. Both were concluded the most effective of the 4 options, pending confirmation in a larger group.

In 2022, a systematic review and meta-analysis from Spain pooled randomized trials of photobiomodulation (PBM) for pain and oral quality of life in burning mouth syndrome. From 103 records, 7 randomized trials were included, using red light between 630 and 685 nanometres or infrared light between 810 and 830 nanometres against a switched-off laser or a drug, over courses of 14 to 70 days. Researchers found that the PBM groups showed a greater fall in pain than the control groups by the end of treatment, and a larger gain in quality of life related to oral health. Split by wavelength, infrared light differed significantly from control, while red light did not.

Comparing photobiomodulation therapy (PBMT) against sham or drug treatment across 12 studies, a 2021 systematic review and meta-analysis from Italy examined the neurological form of primary burning mouth syndrome (BMS). The included studies used wavelengths from 635 to 980 nm and power outputs from 30 mW to 4 W, and the reviewers judged 7 of the 12 to be poorly designed enough that their results could not be fully trusted. When 4 of the better studies were pooled, patients who received PBMT reported significantly less pain than those who received sham or drug treatment. The authors concluded that PBMT may help neurological BMS, but that the weakness of most of the studies means firmer trials are needed before that can be relied on.

Across 574 patients in 12 randomized trials, a 2021 meta-analysis from China assessed photobiomodulation (PBM) for primary burning mouth syndrome (BMS). Searches of Chinese and English databases up to February 2020 found the 12 trials, 5 of which supplied pain data for pooling and 4 quality-of-life data, with 3 more comparing PBM against medication. According to the analysis, PBM reduced pain compared with placebo and improved quality of life, and the included trials suggested it may also lower 2 inflammation markers in saliva. None of the trials reported a treatment-related adverse event.

9 of the 10 patients who received photobiomodulation (PBM) still had less pain 4 months after treatment in a 2020 randomized controlled trial of burning mouth syndrome (BMS) in Spain. 20 patients took part, with the treatment group of 10 receiving 810 nm light at 600 mW, 1200 mW/cm² and 12 J/cm², 6 J per point for 10 seconds in contact with the affected sites, over 5 weeks. Researchers found that every patient in the treatment group had less pain by the end of the course. Significant gains also appeared on parts of a pain questionnaire, a sleepiness scale and a psychological symptom checklist, at the end of treatment and at 1 and 4 months.

Published in 2020, this randomized controlled trial in Italy used photobiomodulation therapy (PBM) with a diode laser on the lining of the mouth in burning mouth syndrome (BMS), and then examined the tiny blood vessels beneath it with a magnifying camera. 40 patients were split evenly into a laser group receiving 8 sessions of 800 nm light at 4 W and 50 J/cm², delivering 1200 J over 300 seconds from about 4 cm away, and a placebo group of 20. Average pain ratings fell from 7 to 3 in the laser group and from 7 to 5 in the placebo group by the 8th session, and after a further observation period the placebo group had returned to 7 while the laser group stayed at 3, the researchers reported. In the laser group, the tiny blood vessels became narrower and longer in every treated region, changes the placebo group did not show.

Across 85 patients recruited over 3 years, a 2019 randomized controlled trial in Italy tested photobiomodulation therapy (PBMT) against a sham treatment for burning mouth syndrome. 43 patients received light from a multi-wavelength device at 660 to 970 nm and 3.2 to 6.4 W, pulsed at 1 to 20000 Hz, for 3 minutes 51 seconds per session once a week for 10 weeks, while 42 received sham sessions, with pain and oral quality of life assessed at the start and after every session. Symptoms decreased significantly and quality of life related to oral health improved in the PBMT group, suggesting a real benefit. The researchers described a positive effect on both symptoms and overall quality of life.

A double-blind design was used in a 2019 randomized controlled trial of low-level laser therapy (LLLT) for burning mouth syndrome (BMS). 21 patients were assigned to a laser group of 12, receiving 808 nm light at 200 mW, 1970 mW/cm², and 3 J per point for 15 seconds per point on each site with symptoms, twice a week for 4 weeks, or to a control group of 9. Burning scores on a standard rating scale started at an average of 8.9 in the laser group and 8.3 in the control group. The trial found that LLLT may be an alternative treatment for relieving the burning. No side effects were recorded.

2018 brought a randomized controlled trial in Brazil that set low level laser therapy (LLLT) against alpha-lipoic acid (ALA) for burning mouth syndrome and for oral burning caused by other conditions. 44 patients, 81.8% of them women and 72.2% of the women in or past menopause, with an average age of 60.2, were split into 4 groups, 10 with burning mouth syndrome and 15 with secondary burning receiving 660 nm light at 30 mW and 3 J/cm² for 10 seconds per site once a week for 4 weeks, and 5 and 14 receiving ALA, alongside 8 healthy women as a comparison. Saliva flow increased only in the burning mouth syndrome patients and only after the laser, while symptoms eased in both conditions with both treatments, the researchers reported. An inflammation marker in saliva did not differ between groups or change with treatment, and the trial concluded LLLT the more efficient of the 2 therapies.

According to a 2017 review, researchers assessed low-level laser therapy (LLLT) for burning mouth syndrome across every clinical study they could find up to October 2016. 10 clinical studies met the criteria, 5 of them randomized trials, using wavelengths from 630 to 980 nm, power outputs from 20 to 300 mW, and session lengths from 10 seconds to 15 minutes, and the reviewers pooled no statistics because the studies differed too much. Most studies reported laser as an effective way to manage the condition. The authors concluded that laser therapy seemed to reduce pain in these patients, but because the 10 studies used different designs and different laser settings, more trials are needed before anyone can say how well it works.

Pain scores improved by 15.7% and 15.6% in 2 laser groups against 7.3% with a placebo, in a 2017 partially blinded randomized clinical trial of low-level laser therapy (LLLT) for burning mouth syndrome (BMS) in Spain. The study split 44 patients into 3 groups: 16 received 815 nm light at 1 W for 4 seconds and 4 J per point at 133.3 J/cm², 16 received the same light for 6 seconds and 6 J at 200 J/cm², and 12 received a sham laser, all once a week for 4 weeks. Pain was rated on a standard scale, alongside questionnaires on oral quality of life, dry mouth, and anxiety and depression. Both laser groups appeared to improve more than the placebo group over the first 2 weeks, but no statistically significant difference emerged between weeks 2 and 4.

This 2016 review from India surveyed photobiomodulation (PBM), also called low level laser therapy (LLLT), across its uses in oral medicine, burning mouth syndrome among them. It outlined how the light is thought to act on cells and then summarised the clinical studies for each application, from mouth ulcers and cold sores to jaw joint pain. The authors concluded that well-documented research confirms PBM's value in a few conditions, burning mouth syndrome, oral mucositis and recurrent cold sores among them, but that the shortage of standardised studies and the confusion over laser settings limit its credibility elsewhere. The reviewers noted the absence of any reported adverse effects as an advantage over conventional treatments.

Comparing low-level laser therapy (LLLT) with clonazepam tablets dissolved in the mouth, a 2016 randomized controlled trial in Italy examined burning mouth syndrome in 33 patients. The 25 women and 8 men, with an average age of 67.12, were split into a laser group of 18 receiving 980 nm light at 300 mW, 10 J/cm², and about 1000 mW/cm², held 2 mm from the lining of the mouth, twice a week for 5 weeks, and a drug group of 15 taking half a 2 mg clonazepam tablet held in the mouth for three minutes, three times daily over 3 weeks. 12 weeks after treatment ended, the laser group reported less pain on all 4 measures used, while the clonazepam group improved on fewer of them. The difference between the groups reached statistical significance only at 8 weeks after treatment, and anxiety and depression levels did not change in either group.

A 2015 randomized controlled trial in Iran evaluated low-level laser (LLL) treatment against a switched-off placebo for the symptoms of burning mouth syndrome. 20 patients were randomly split into 2 groups, with the laser group receiving 630 nm light at 30 mW over 10 seconds at each of 10 areas on the lining of the mouth, twice a week for 4 weeks, and the placebo group receiving the same routine with the laser switched off. According to the trial, both burning severity and quality of life differed significantly between the groups after treatment, in favor of the laser group. The conclusion was worded cautiously, saying low-level laser might decrease the intensity of the condition.

Infrared light at 830 nm given once or 3 times a week, red light at 685 nm, and a sham laser were compared in a 2015 randomized controlled trial of low-level laser therapy (LLLT) for burning mouth syndrome in Brazil. 78 patients, 67 women and 11 men with an average age of 62.82, were assigned to 4 groups, with 20 receiving 830 nm light at 100 mW, 3570 mW/cm², 5 J and 176 J/cm² for 50 seconds per point once a week for 10 sessions, 20 receiving the same dose 3 times a week for 9 sessions, 19 receiving 685 nm light at 35 mW, 1250 mW/cm², 2 J and 72 J/cm² for 58 seconds per point 3 times a week for 9 sessions, and 19 receiving 9 sham sessions. Symptoms tended to fall in every group by the end of treatment and stayed lower 8 weeks later, but only the 2 infrared groups differed significantly from the sham group. Quality of life related to oral health also improved in all 4 groups, with the 3-times-a-week infrared group the only 1 to differ significantly from sham.

18 of 20 volunteers with burning mouth syndrome showed lower burning scores after laser phototherapy (LPT) in a 2015 clinical trial in Brazil. The volunteers, mostly women over 50, had first spent two and a half months on conventional treatment including artificial saliva, pilocarpine, clonazepam and fluoxetine, and then received 660 nm light at 40 mW, 10 J/cm² and 0.4 J per point for 10 seconds per point, once a week for 10 weeks. Burning scores on a standard scale fell by up to 49% by the final laser session, against a fall of no more than 4% during the drug phase. The study found the reduction was statistically significant in almost every session compared with the first.

3 patients with burning mouth syndrome (BMS) who received high-power pulsed near-infrared light to the base of the neck all showed lower tongue pain scores in a 2014 case series from Japan. The linearly polarized light at 780 to 1400 nm was delivered at 5 W for 3 minutes per session over a nerve cluster at the base of the neck, with pain rated on a standard scale and heart rhythm patterns used to track the body's automatic nerve response. Pain scores appeared to fall significantly in every case, and in most cases the heart rhythm readings changed in the same direction as the pain, so the 2 tracked each other. No adverse events such as heat injury occurred.

Applying a pulsed 800 nm diode laser directly to the painful areas of the tongue, a 2011 case series in Taiwan treated 17 patients with burning mouth syndrome. The laser ran at 3 W in 50-millisecond pulses at 10 Hz, an average of 1500 mW/cm², and each 1 cm² area received 70 seconds at 105 J/cm² until every affected area was covered, with patients treated between 1 and 7 times. Pain scores on a standard rating scale started at an average of 6.7 and fell by an average of 47.6%, with individual reductions ranging from 9.3% to 91.8%. The burning appeared to stay at the reduced level for up to 12 months.

10 patients with burning mouth syndrome (BMS) took part in a 2011 case series in Brazil testing low-level laser therapy (LLLT). Each received 660 nm light at 40 mW and 20 J/cm², with 0.8 J delivered per point over 10 seconds in contact with the tongue, lips, inside of the cheeks, and roof of the mouth, in 1 session a week for 10 weeks. According to the study, every patient reported improvement at every session, and scores on a standard burning rating scale fell by up to 58% by the 10th session. Compared with the first session, the reduction was statistically significant from the 4th session onward.

25 patients with the neurological form of burning mouth syndrome (BMS), 16 women and 9 men, took part in a 2010 clinical trial in Italy of low level laser therapy (LLLT). They were selected from 77 such patients identified among 160 people with oral burning, and each received a dual diode laser emitting 650 nm and 910 nm at the same time, at 0.53 J/cm², on the sides of the tongue for 15 minutes, twice a week for 4 weeks. According to the trial, 17 of the 25 patients, or 68%, gained a meaningful reduction on a standard 0 to 10 pain scale, 8 showed changes too small to count, and nobody got worse. The reduction in worst pain reached statistical significance while the change in least pain did not. No side effects were recorded and every patient completed the course.

Patients reported an 80.4% reduction in burning intensity after infrared low-level laser therapy (LLLT) in a 2010 pilot clinical trial for burning mouth syndrome (BMS) in Brazil. 11 patients with 25 affected sites across the tongue, lips, and roof of the mouth received 790 nm light at 120 mW and 6 J/cm², with the probe held in contact with the tissue and moved across the surface, once a week for 3 weeks. The trial found burning intensity on a standard rating scale was statistically lower at the end of treatment than at the start. The improvement held at a 6-week follow-up at every site except the tongue.

75.7% of 37 patients with tongue pain reported less pain after near-infrared light to the base of the neck in a 2004 clinical trial from Japan. The diagnosis in this study is glossodynia, the tongue pain grouped on this tab under burning mouth syndrome (BMS), and the light was applied at 600 to 1600 nm and 1.5 W for 10 minutes over a nerve cluster at the base of the neck, at 194.8 J/cm², once a week for 4 weeks, with 8 healthy people as a comparison for blood flow. Researchers found that pain intensity fell from an average of 5.1 to 1.9 on a standard scale, with 28 of the 37 patients improving. Blood flow in the tongue, which had been lower in the patients than in the healthy group, rose within 5 minutes of the first session along with a 1.5 °C rise in tongue temperature, and was still higher after 4 weeks.

1990 brought a clinical trial of infrared soft laser treatment for the burning and pain of burning mouth syndrome. 70 patients took part, with 40 receiving the 904 nm laser at 20 W for 3 minutes per 1 cm² of the lining of the mouth on 5 consecutive days, and a comparison group of 30 receiving a drug that widens blood vessels, delivered through the tissue with a small electric current. Pain relief appeared after the first laser session and burning intensity tended to fall each day of treatment, with the before-and-after difference reaching statistical significance. Tissue temperature rose by only 0.1 °C during treatment, a change the trial did not find meaningful.

Pain scores fell from 7.80 to 2.07 immediately after each session of photobiomodulation (PBM) in a 2024 clinical trial of burning mouth syndrome (BMS) in Israel. 30 patients received 940 nm light at 3 W inside the mouth once a week for up to 10 weeks, with pain rated on a standard scale straight after each session and as a weekly average. By the week after the final session the average score had climbed back to 5.73, still below the starting level but well above the immediate response, the researchers reported. Relief tended to grow with repeated sessions, though only up to the 3rd, and men and patients with pain on 1 side only appeared to respond better.

Low-level laser therapy (LLLT) and a drug combination did the most for quality of life related to oral health, according to a 2024 review of treatments for burning mouth syndrome (BMS) from Portugal. From 5400 records, 13 studies were included, with general quality of life measured by a standard health survey and oral quality of life by 2 standard questionnaires, covering treatments that ranged from drugs to laser. According to the review, most treatments improved general quality of life, but LLLT and N-acetylcysteine plus clonazepam stood out for oral quality of life. The variation between studies led the reviewers to call for consistent trial designs before any treatment can be concluded as reliably effective.

In 2023, a systematic review and meta-analysis from China pooled 14 randomized trials of low level laser therapy (LLLT) for burning mouth syndrome (BMS). The trials covered 550 patients and compared LLLT against placebo laser or clonazepam, with burning pain, oral quality of life and anxiety and depression as the outcomes. LLLT appeared more effective than placebo or clonazepam at reducing burning pain, a difference that was statistically significant. Quality of life and mood moved in the right direction too, but neither change reached significance.

Whether low level laser therapy relieves the symptoms of burning mouth syndrome was the question a 2021 review from Brazil put to 8 randomized trials. The trials covered 314 patients, mostly women with an average age of 60.89, of whom 191 received the laser and 123 a switched-off or blocked device, over courses of 2 to 10 weeks with symptoms rated on standard scales. Only 3 of the 8 trials showed a statistically significant result, and the reviewers described the laser settings as varied and often incompletely reported. Laser therapy may be an effective alternative for the condition, the review suggested, provided future trials adopt well-established protocols.

This 2013 single-arm clinical study in Japan asked whether tracking heart rhythm variation could reveal the nerve imbalance linked to burning mouth syndrome (BMS) and show whether near-infrared light corrected it. 8 patients received 780 to 1400 nm light at 1.32 W, pulsed at 0.2 Hz, for 10 minutes per session, aimed at a nerve cluster at the base of the neck, with their heart rhythm patterns recorded before and after each session. The usual heart rhythm measures could not tell which patients improved with the light and which did not. Researchers found that comparing each patient's heart rhythm just before and just after a session did capture the light's effect, and they suggested this simple before-and-after comparison could be used to follow BMS patients and judge whether the light therapy is working.

Whether low-level laser therapy (LLLT) changes the level of 2 inflammation markers in saliva was examined in a 2013 clinical trial of burning mouth syndrome in Croatia. 40 patients, 27 women and 13 men with an average age of about 60, were split into a laser group of 20 receiving 685 nm light at 30 mW and 3 J/cm² on the tongue for 10 minutes per session over 4 weeks, and a placebo group of 20 treated with the same device switched off. Only the laser group showed a statistically significant drop in both saliva markers, while the placebo group showed no meaningful change. Pain ratings on a standard scale moved from 7 to 6 in the laser group, a change that was not statistically significant. The authors concluded that the drop in inflammation markers corresponded to clinical improvement, even though the change in pain scores fell short of significance.

No statistically significant difference in pain reduction separated the light group from the sham group at any point in a 2024 single-blind controlled clinical trial of photobiomodulation (PBM) for burning mouth syndrome (BMS) in Brazil. 30 patients were assigned in turn to PBM or sham, with the PBM group receiving 660 nm light at 100 mW and 6 J/cm² for 10 seconds per point across each 1 cm² of symptomatic tissue, once a week for 10 sessions. Maximum pain intensity nonetheless appeared to fall by 50% in both groups compared with what patients reported before treatment. The trial calls for larger studies with random assignment with longer follow-up to understand the placebo effect seen here.

When researchers measured a stress hormone in saliva alongside burning symptoms, a 2020 double-blind randomized controlled trial in Croatia found that both fell whether patients received low-level laser therapy (LLLT) or a placebo for burning mouth syndrome. 23 patients were randomly split into a laser group of 12 receiving 685 nm light once a day for 10 consecutive weekdays and a placebo group of 11 treated with an inactive probe that only made a sound, with burning rated on a standard scale and saliva collected at the start and on the last day. According to the trial, burning scores and saliva stress hormone levels were significantly lower in both groups at the end of the course. Whether the result reflects the laser or a placebo effect remains open, with the trial calling for larger studies.

Among 44 patients, 43 of them women, aged 56 to 83 with an average age of 67.56, a 2018 single-blinded randomized trial in Croatia compared low level laser therapy (LLLT) switched on against the same device switched off for burning mouth syndrome (BMS). Groups were assigned by coin toss, and the laser group received 830 nm light at 100 mW and 12 J/cm² held about 5 mm from the burning site, in 10 sessions over 10 days, with pain and oral quality of life rated before and after. Pain scores appeared to fall significantly in both the laser-on and the laser-off groups. Neither group showed any change in quality of life related to oral health.

No advantage over placebo emerged for low intensity laser therapy in a 2016 randomized placebo-controlled trial of burning mouth syndrome in Brazil, except at 2 of the follow-up checkpoints. 30 patients were randomized and 23 completed, 13 in the laser group and 10 in the placebo group, with each receiving 4 sessions twice a week for 2 weeks of 790 nm light at 20 mW and 6 J/cm², moved across the affected lining of the mouth, and burning rated on a standard scale before and after each session and at follow-up checks from 1 week to 3 months after the last session. The trial found the laser group did statistically better in only 2 of the checkpoint categories, and concluded that the laser was as beneficial as placebo under this protocol. At 3 months, 46% of the laser group and 40% of the placebo group reported no burning at all.