Red Light Therapy Frequencies: Hz & Pulse Modes

Most red light therapy discussions focus on wavelength — 630nm versus 850nm, red versus near-infrared. But there is a second variable that receives far less attention: frequency, measured in hertz (Hz). This refers to whether the light is delivered as a continuous beam or pulsed on and off at a specific rate.

The question matters because pulsed light and continuous wave (CW) light interact with tissue differently. Some researchers believe pulsing unlocks biological effects that continuous exposure cannot. Others argue the evidence is too thin to justify the added complexity. This article examines what we actually know.

Continuous Wave vs Pulsed Light

Continuous wave (CW) means the LED or laser emits light at a constant intensity for the entire treatment duration. The power output does not fluctuate. This is how the vast majority of consumer red light therapy panels operate.

Pulsed light means the source switches on and off at a defined rate. A device pulsing at 10 Hz turns on and off ten times per second. The pulse can be square-wave (instant on, instant off) or shaped, though most consumer devices use square-wave patterns.

Three parameters define pulsed delivery:

Frequency (Hz) — how many on-off cycles occur per second
Duty cycle (%) — the proportion of each cycle spent in the “on” state. A 50% duty cycle at 10 Hz means the light is on for 50 milliseconds and off for 50 milliseconds in each 100ms cycle
Peak irradiance — the power density during the “on” phase, which is typically higher than the average irradiance

At a 50% duty cycle, the average dose delivered is half that of continuous wave at the same peak irradiance. This is important: if you simply pulse a device without increasing peak power, you deliver less total energy per session.

The Biological Rationale for Pulsing

Cellular Rest Periods

One hypothesis is that cells need brief recovery intervals during photobiomodulation, and that the off periods in pulsed light allow this. It remains a hypothesis. The main review of the topic, Hashmi et al. (2010, Lasers in Surgery and Medicine; PMID: 20662021), surveyed the literature from 1970 to 2010, including studies that compared pulsed and continuous light in animals and patients. It concluded that there is some evidence pulsed light has effects that differ from continuous light, but that further work is needed to define those effects for different conditions and pulse structures.

None of this has been demonstrated in human tissue at the power densities used in consumer devices.

Nitric Oxide Release

Nitric oxide (NO) is one of the mitochondrial signalling elements that red and near-infrared irradiation modulates, with cytochrome c oxidase considered the photoacceptor (Karu, 2008, Photochemistry and Photobiology; PMID: 18651871). It has been suggested that pulsed delivery could change the pattern of NO release, but that review does not test pulsing, and we found no study showing a clinically meaningful difference from continuous light.

Resonance With Biological Oscillations

Perhaps the most intriguing rationale is that specific pulse frequencies may resonate with endogenous biological rhythms — brainwave oscillations, cellular calcium signalling cycles, or mitochondrial membrane potential fluctuations. This is where specific Hz values enter the conversation.

10 Hz: Popular, but Not Established

10 Hz is the pulse rate most often marketed for tissue repair, and it falls within the alpha range of brain oscillations, which is where much of the resonance argument comes from. We did not find a primary study showing that 10 Hz outperforms continuous light or other frequencies for wound healing. Hashmi et al. (2010), often cited for this, is a literature review, not an experiment, and it does not single out 10 Hz as best (PMID: 20662021).

The closest primary data are in cell culture. Brondon et al. (2009) in Lasers in Surgery and Medicine irradiated human HEP-2 cells with 670nm light through a melanin filter, either unpulsed or pulsed at 6, 18, 36, 100 or 600 Hz. All frequencies stimulated the cells at 48 and 72 hours; proliferation peaked at 100 Hz and oxidative burst at 600 Hz. The study did not test 10 Hz and was designed to ask whether pulsing helps light get past skin pigment (PMID: 19291749).

Clinical relevance: There is no verified evidence that 10 Hz pulsing improves wound healing, tissue repair or skin outcomes in people. If your goal is one of these, continuous wave is the better-documented choice.

40 Hz: Gamma Entrainment and Neurological Applications

The 40 Hz frequency has gained significant attention following groundbreaking work by Iaccarino et al. (2016) published in Nature. The MIT researchers showed that a 40 Hz light-flicker regime reduced amyloid-beta levels in the visual cortex of Alzheimer’s model mice before plaques formed, and reduced plaque load in older mice that already had plaques (PMID: 27929004).

Subsequent work by the same group (Martorell et al., 2019, Cell; PMID: 30879788) showed that 40 Hz sound stimulation improved spatial and recognition memory and reduced amyloid in Alzheimer’s model mice, and that combining 40 Hz sound with 40 Hz light, but not either alone, reduced amyloid in the medial prefrontal cortex and produced widespread plaque reduction across the neocortex.

How 40 Hz Works

Forty hertz corresponds to the gamma frequency band of neural oscillation. Gamma oscillations are associated with attention, memory consolidation, and information processing. In Alzheimer’s disease, gamma oscillatory activity is disrupted. The theory is that entraining the brain to 40 Hz via flickering light:

Recruits microglia to clear amyloid plaques
Modifies neural circuit activity
Enhances cerebrospinal fluid clearance of waste products
Improves vascular function in the brain

Human Trial Data

The GENUS (Gamma ENtrainment Using Sensory stimulation) clinical trials at MIT have tested 40 Hz light flicker in human Alzheimer’s patients. Published feasibility and Phase 2A pilot results found that daily 40 Hz light-and-sound stimulation for three months was safe and well-tolerated, with the stimulated group showing less ventricular dilation and hippocampal atrophy, better performance on a delayed recall test, and improved daily activity rhythmicity than the control group (Chan et al., 2022, PLoS One; PMID: 36454969).

However, it is crucial to understand that this research uses visual flicker — light perceived through the eyes — not transcranial photobiomodulation applied to the scalp. The mechanism is neural entrainment via the visual pathway, not direct tissue photobiomodulation. Consumer red light therapy panels applied to the body would not replicate this effect.

Some transcranial PBM devices do offer 40 Hz pulsing applied to the scalp, which represents a different (and less well-evidenced) approach. The Vielight Neuro Gamma is one such device specifically designed for 40 Hz transcranial delivery.

Clinical relevance: 40 Hz is relevant primarily for neurological applications delivered via visual flicker or transcranial devices. It does not apply to general body-panel red light therapy.

Other Frequencies in Research

100 Hz and 1 kHz Pulse Modes

Lapchak et al. (2007) tested transcranial near-infrared light therapy in a rabbit embolic-stroke model, comparing continuous wave against two pulsed regimens (a 2ms pulse at 100 Hz and a 300-microsecond pulse at 1 kHz). Given 6 hours after embolization, both pulsed modes produced a statistically significant improvement in behavioural outcome, while CW showed only a non-significant trend (PMID: 17693028). Transcranial near-infrared laser therapy for stroke was separately tested in the NEST (NeuroThera Effectiveness and Safety Trial) clinical trials for acute ischaemic stroke, though the Phase III trial ultimately failed to meet its primary endpoint.

100 Hz and Above

Higher frequencies (100–1000 Hz) appear in some wound healing and pain research, but the evidence is inconsistent. At very high frequencies, the biological effect may approximate CW because the on-off cycling exceeds the temporal resolution of cellular responses.

292 Hz

Used in some dental photobiomodulation studies for accelerating orthodontic tooth movement. Niche application with limited broader relevance.

The Evidence Is Mixed — Here Is Why

Despite promising individual studies, the reviews paint a cautious picture. Hashmi et al. (2010) found only “some evidence” that pulsed light behaves differently from continuous light and called for further work to define the effects for different conditions and pulse structures (PMID: 20662021). There is no verified single “best” frequency for all applications.

Several factors complicate the evidence:

Dose confounding. Photobiomodulation shows a biphasic dose response, with different effects as energy density changes (Huang et al., 2011, Dose-Response; PMID: 22461763). If a pulsed group receives less total energy because of the duty cycle, any difference in outcomes could reflect dose rather than pulsing itself.

Lack of standardisation. Studies vary enormously in pulse parameters — frequency, duty cycle, peak power, total energy, wavelength, treatment area, and duration. This makes cross-study comparison nearly impossible.

Publication bias. Positive results showing pulsed superiority are more likely to be published than null findings showing no difference from CW.

Animal vs human translation. Most of the evidence for pulsed advantages comes from cell culture and animal models. Mouse skin, wound healing, and neural tissue differ substantially from human equivalents.

Duty Cycle: The Overlooked Variable

Even when a frequency is specified, the duty cycle dramatically affects the treatment. Consider 10 Hz at three different duty cycles:

Duty Cycle	On Time	Off Time	Average Power (vs CW)
50%	50 ms	50 ms	50%
30%	30 ms	70 ms	30%
80%	80 ms	20 ms	80%

At 30% duty cycle, you are delivering less than a third of the energy of continuous wave in the same treatment duration. To match CW total dose, you would need to either increase peak power or extend treatment time proportionally.

Most consumer devices that offer pulsing use a 50% duty cycle by default. Some allow adjustment, but few provide guidance on which duty cycle to select for which purpose.

Which Consumer Devices Offer Pulse Mode?

Not all red light therapy panels include pulsing capability. Devices that do include:

Mito Red Light — MitoPRO and MitoADAPT series offer adjustable pulse frequencies (10 Hz, 40 Hz, 73 Hz, 146 Hz, 292 Hz, 584 Hz, and 1168 Hz)
Hooga — Some models include pulse mode at 10 Hz
PlatinumLED BioMAX — Offers pulsing functionality
Kineon Move+ — Uses pulsed laser and LED combination, reportedly at 10 Hz
Vielight — Transcranial devices with 10 Hz (Alpha) and 40 Hz (Gamma) modes, designed specifically for neural applications

Many popular panels from Joovv, Rouge, and BestQool operate exclusively in CW mode. This is not necessarily a disadvantage — continuous wave has the largest overall evidence base in photobiomodulation research.

When to Use Continuous Wave vs Pulsed

Based on the current evidence, here is a practical framework:

Use Continuous Wave When:

You are targeting skin conditions (wrinkles, acne, wound healing) — most dermatological studies used CW
You want simplicity and do not wish to navigate pulse parameter selection
Your primary goal is collagen production, inflammation reduction, or general recovery
You are following a protocol based on published research that used CW delivery

Consider Pulsed Mode When:

Your device supports it and you want to experiment, knowing the evidence for any specific frequency is preliminary
You are willing to extend treatment time to compensate for reduced average dose

Consider 40 Hz When:

You are using a transcranial PBM device for cognitive or neurological purposes
You are following a protocol specifically designed for gamma entrainment
Do not use 40 Hz body panels expecting neurological benefits — the mechanism requires visual or transcranial delivery

Stick With CW If Unsure

If you are uncertain, CW is the safer default. It has decades of research behind it across hundreds of clinical trials. The potential advantage of pulsing is marginal in most applications and comes with the risk of under-dosing if duty cycle is not properly accounted for.

Common Misconceptions

“Pulsed light penetrates deeper than CW.” There is no strong evidence for this. Penetration depth is primarily a function of wavelength and tissue optical properties, not pulse frequency. Some studies suggest pulsed delivery may improve energy deposition at depth due to thermal relaxation between pulses, but this applies primarily to high-powered lasers, not LED panels.

“NASA proved that pulsing is better.” Whelan et al. reported on LEDs originally developed for NASA plant-growth experiments, presenting cell culture data, rat wound models and human reports that included Navy SEAL training injuries and wounds in submarine crew. This is the origin of the “NASA LED” claim seen on many red light therapy sites, but the paper is not a pulsed-versus-CW comparison and does not support a pulsing-is-better conclusion (Whelan et al., 2001, Journal of Clinical Laser Medicine & Surgery; PMID: 11776448).

“Higher frequency means faster results.” There is no verified linear relationship between pulse frequency and treatment efficacy. In the one cell study above, different frequencies peaked for different outcomes (100 Hz for proliferation, 600 Hz for oxidative burst), which is a reason for caution rather than a rule.

Practical Recommendations

Do not pay a premium solely for pulse capability unless you have a specific evidence-based reason to use it. CW devices deliver excellent results across the majority of studied applications.
If your device has pulse mode and you want to try it, remember that a 50% duty cycle halves the average dose, so double the treatment time to match a continuous-wave session. No specific frequency has verified human evidence for tissue repair.
For neurological applications, invest in a purpose-built transcranial device (e.g., Vielight Neuro Gamma at 40 Hz) rather than attempting to repurpose a body panel.
Keep records. If you experiment with pulsed modes, track your parameters (frequency, duty cycle, treatment time) and outcomes. Individual responses vary, and self-tracking is the only way to determine what works for your specific situation.
Watch the research. Pulsed PBM is an active area of investigation. The GENUS trials for Alzheimer’s disease are particularly promising and may reshape how we think about frequency-specific light therapy over the coming years.

Summary

Pulse frequency is a genuine variable in photobiomodulation, but its practical importance for the average user is overstated by marketing. The most developed frequency-specific evidence is for 40 Hz gamma entrainment via light and sound flicker in Alzheimer’s research (a distinct mechanism requiring visual or auditory delivery, still at pilot stage in humans). The popular 10 Hz setting for wound healing has no verified trial behind it. For most applications (skin health, pain relief, muscle recovery, joint support), continuous wave delivery remains the best-evidenced approach. If your device offers pulsing, it is worth experimenting with, but it should not be the primary factor driving your purchase decision.

References

Hashmi JT, et al. Effect of pulsing in low-level light therapy. Lasers Surg Med. 2010;42(6):450-466. PMID: 20662021
Iaccarino HF, et al. Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature. 2016;540(7632):230-235. PMID: 27929004
Martorell AJ, et al. Multi-sensory gamma stimulation ameliorates Alzheimer’s-associated pathology and improves cognition. Cell. 2019;177(2):256-271. PMID: 30879788
Brondon P, et al. Pulsing influences photoradiation outcomes in cell culture. Lasers Surg Med. 2009;41(3):222-226. PMID: 19291749
Huang YY, et al. Biphasic dose response in low level light therapy, an update. Dose Response. 2011;9(4):602-618. PMID: 22461763
Karu TI. Mitochondrial signaling in mammalian cells activated by red and near-IR radiation. Photochem Photobiol. 2008;84(5):1091-1099. PMID: 18651871
Lapchak PA, Salgado KF, Chao CH, Zivin JA. Transcranial near-infrared light therapy improves motor function following embolic strokes in rabbits: an extended therapeutic window study using continuous and pulse frequency delivery modes. Neuroscience. 2007;148(4):907-914. PMID: 17693028
Whelan HT, et al. Effect of NASA light-emitting diode irradiation on wound healing. J Clin Laser Med Surg. 2001;19(6):305-314. PMID: 11776448
Chan D, et al. Gamma frequency sensory stimulation in mild probable Alzheimer’s dementia patients: results of feasibility and pilot studies. PLoS One. 2022;17(12):e0278412. PMID: 36454969