A Brief History of Photobiomodulation (PBM): From Laser to LED, From Laboratory to Living Room

The Beginning: A “Failed” Experiment in Hungary, 1967

In 1967, Professor Endre Mester at Semmelweis University in Hungary was investigating the effects of lasers on biological tissues. He shaved the hair off the backs of laboratory mice, exposed one group to a low-power ruby laser ($694\text{ nm}$), and observed the results.

He expected to see whether the laser induced tissue damage or cancer.

What he actually saw was that the mice irradiated by the laser grew their back hair significantly faster than the control group.

Mester’s initial reaction was likely to check the data for errors, but repeated experiments confirmed this accidental discovery. It was not a case of the laser damaging tissue; rather, a specific wavelength of light delivered at a low power was triggering a biological response without generating thermal effects.

He termed this phenomenon “Laser Biostimulation.” The nomenclature underwent several iterations over the decades—from Low-Level Laser Therapy (LLLT) to Cold Laser, and was ultimately unified by the scientific community in the 2010s as Photobiomodulation (PBM). The consensus shifted because the underlying mechanism is independent of “lasers” or “low levels”—it is fundamentally the modulation of biological processes by light, whether generated by a laser or an LED.

Mester could not have known that his “failed” experiment in 1967 would cascade over the next half-century, moving from a Hungarian lab to NASA space capsules, and eventually into LED face masks found in living rooms worldwide.

1970s–1990s: The Laser Era — From Curiosity to Clinical Application

1970s–1980s: Uncovering the Foundational Mechanism

Mester’s findings sparked global research interests. The core of the investigation shifted to determining exactly why light accelerates healing and which wavelengths are effective.

In the 1980s, Cytochrome c Oxidase (CCO) was identified as the primary photoacceptor within mitochondria, particularly for wavelengths in the red ($\sim 620{-}670\text{ nm}$) and near-infrared (NIR, $\sim 780{-}940\text{ nm}$) ranges. CCO is Complex IV in the mitochondrial electron transport chain. It transfers electrons to oxygen to form water and pumps protons across the membrane to drive the synthesis of adenosine triphosphate (ATP), the cell’s energy currency.

The absorption of photons alters CCO activity, increasing mitochondrial membrane potential and boosting ATP production while modulating intracellular levels of reactive oxygen species (ROS) and nitric oxide (NO). This milestone answered the most fundamental question of PBM—moving the field beyond mere observation and explaining precisely where the biological effect originates.

Other discoveries made during the 1980s and 1990s included:

• Red and NIR light promote fibroblast proliferation and collagen synthesis, explaining the mechanisms behind wound healing and tissue repair.

• PBM exhibits neuroprotective effects on nervous tissues, planting the seed for later applications in pain management and neuroscience.

• The Biphasic Dose Response was documented: doses that are too low yield no effect; appropriate low doses stimulate biological activity; doses that are too high either yield no effect or cause inhibition (early evidence of the “biological switch” phenomenon).

1990s: NASA Intervenes — From Deep Space to Critical Care

In the 1990s, NASA faced a persistent challenge: in zero-gravity environments, astronauts experienced significantly slower wound healing, muscle atrophy, and bone density loss. Traditional treatments were slow, and drug metabolism in space differed from that on Earth.

NASA researchers explored a biological hypothesis: if Cytochrome c Oxidase absorbs red and NIR light to increase ATP and accelerate cellular metabolism, it could theoretically counteract metabolic deceleration caused by space environments.

In 1995, NASA initiated research into “space medicine PBM,” utilizing LED arrays rather than lasers. LEDs were chosen because they are lighter, consume less power, produce negligible waste heat, and can cover large surface areas. This research investigated PBM’s potential to accelerate wound healing and maintain muscle and bone health during space travel.

NASA’s involvement accelerated two major breakthroughs:

1. Validating LEDs as viable PBM light sources: Prior to NASA, PBM relied almost exclusively on lasers (monochromatic, coherent light). The polychromatic and incoherent nature of LEDs was assumed to be theoretically less effective. However, NASA verified in cellular and animal models that incoherent light from LEDs achieves equivalent therapeutic efficacy to coherent laser light under bio-equivalent dosing.

2. Amplifying PBM’s value as a non-pharmaceutical, non-invasive intervention: Following NASA’s publications, the academic scope of PBM research expanded rapidly across disciplines—from dentistry and neuroscience to sports medicine and dermatology.

2000s–2010s: The LED Revolution — LEDs Ascend as Primary Light Sources

The NASA WARP 75 Project and the Birth of Handheld Devices

In the early 2000s, NASA licensed its LED-array-based phototherapy technology through its technology transfer program, driving commercialization. Early commercial devices were handheld, resembling small searchlights. They were deployed to treat oral mucositis (one of the most debilitating side effects of chemotherapy in cancer patients), joint pain, and wounds. The core light source of these devices transitioned definitively from lasers to LEDs.

The operational advantages of high-density LED arrays became clear:

• Coverage: A laser emits a narrow, concentrated beam targeting a singular point. Covering a larger surface area (such as a cheek or a knee) required mechanical scanning or manual clinical application. Conversely, an LED array illuminates an entire surface area simultaneously, making large-area treatments uniform and simple.

• Cost-Efficiency: The manufacturing cost of an LED array is a fraction of an equivalent laser array. This drove down device pricing and expanded market access.

Between 2005 and 2015, published PBM literature grew exponentially, jumping from a few hundred papers annually to over 2,000, with the vast majority utilizing LED arrays.

Key Scientific Consensus Formations (2000s–2010s)

• CCO is not the sole photoacceptor: Beyond CCO, light-sensitive ion channels on cell membranes and opsins were found to play functional roles in PBM, particularly in response to blue and yellow light.

• Quantifying the “Optical Window”: Red light ($600{-}750\text{ nm}$) and near-infrared light ($800{-}950\text{ nm}$) were precisely quantified as the two wavelength bands least absorbed by water molecules in biological tissues, allowing them to achieve maximum penetration depth. Within this window, red light ($620{-}670\text{ nm}$) targets the epidermis and superficial dermis, while NIR ($780{-}850\text{ nm}$) penetrates deeper into subcutaneous tissues and muscle.

• Systematic Validation: PBM’s efficacy was increasingly backed by systematic reviews and meta-analyses across various indications, including pain relief for knee osteoarthritis, prevention of oral mucositis, post-exercise muscle recovery, and androgenetic alopecia.

Evolution of FDA Medical Device Classifications

In the early 2010s, the FDA began clearing LED-based PBM devices as Class II medical devices via the 510(k) pathway for specific indications, such as temporary pain relief, temporary reduction of facial wrinkles, and the treatment of mild-to-moderate acne. Previously, most PBM devices (predominantly lasers) were classified as low-risk Class I tools or Class II energy-saving lasers. Clearing LED PBM devices under the 510(k) pathway signaled that the FDA recognized LED-sourced phototherapy equipment under the same therapeutic regulatory framework as laser systems.

2010s–2020s: The Living Room Era — From Clinical Facilities to Homes

K-Beauty and the Global Explosion of LED Masks ($\sim 2015$–Present)

In the latter half of the 2010s, the South Korean beauty technology sector scaled LED phototherapy for home use. LED face masks, introduced by several Korean brands in the mid-2010s, established a distinct product category: rigid, form-fitting wearable masks lined with dozens or hundreds of red and NIR LEDs. Completed with integrated eye protection, these allowed users to receive treatments at home while relaxing, replacing clinical LED sessions that cost $50 to $200 per visit.

The global growth of the LED mask category exploded between 2020 and 2022. During the COVID-19 pandemic, clinical facility closures drove a surge in demand for home-use beauty devices, establishing LED masks as one of the fastest-growing subcategories in beauty tech.

Category Expansion Beyond the Face

The product architecture of consumer LED PBM devices rapidly expanded beyond facial masks into multiple modalities:

• Handheld Beauty Devices: Targeted, miniaturized tools utilizing red and NIR arrays for localized areas.

• Panels: Desktop and full-body standing panels designed to treat larger surface areas like the chest, back, or thighs.

• Phototherapy Caps: Aimed at hair restoration; following the success of FDA-cleared laser hair caps, LED variants emerged as a more affordable home alternative.

• Neck Devices: Target neck lines and skin laxity, forming a face-and-neck system when paired with a mask.

• Phototherapy Belts: Flexible wraps engineered primarily with NIR LEDs to treat abdominal or lower back chronic pain and support recovery.

• Intraoral Devices: Specialized, niche systems cleared by the FDA to support oral health and gingival tissue maintenance.

Evidence Levels and Limitations of PBM Efficacy

Areas with Robust, Systematic Evidence

• Wound Healing: Backed by broad experimental and clinical literature; forms the earliest evidence base of the discipline.

• Oral Mucositis: Triggered by cancer chemotherapy; possesses the strongest clinical evidence profile and is integrated into clinical guidelines by multiple medical organizations.

• Knee Osteoarthritis Pain: Validated by systematic reviews of multiple randomized controlled trials (RCTs), proving PBM provides pain mitigation superior to sham illumination.

Areas with Moderate, Accumulating Evidence

• Facial Anti-Aging / Wrinkle Reduction: Evidence is derived from small-to-medium RCTs. The directional outcome is consistently positive, though larger sample sizes are required to define long-term parameters and optimal treatment protocols.

• Androgenetic Alopecia: Supported by consistent but limited reviews, mostly historical laser data; LED-specific clinical evidence is steadily expanding.

• Post-Exercise Muscle Recovery: Addressed by numerous small-sample studies showing positive directional effects; however, high study heterogeneity remains, and optimal dosing or wavelength standards are not yet fully unified.

Areas with Weak Evidence or Misaligned Marketing Claims

• Significant Fat Reduction: Direct marketing claims of “fat-burning belts” are not supported by biological mechanisms; PBM does not directly oxidize adipocytes.

• Curing Systemic Diseases: PBM operates via biological modulation rather than the eradication of pathogens. It serves as a supportive, non-curative adjunctive care option and does not replace pharmaceutical or surgical interventions.

Critical Technological Evolution Timeline

Year / Era	Milestone	Significance
1967	Endre Mester discovers low-power ruby lasers stimulate hair growth in mice.	The birth of PBM. An accidental discovery demonstrating non-thermal biological effects of light.
1980s	Cytochrome c Oxidase (CCO) is identified as the primary mitochondrial photoacceptor.	Establishing the biological mechanism. Explained the “why,” providing a molecular target for the rational design of wavelengths and dosages.
1995	NASA initiates LED PBM space medicine research, proving bio-equivalence between LEDs and lasers.	Source diversification. Expanded the PBM light source framework from lasers to LEDs, paving the way for mass consumer adoption.
2000s (Early)	NASA transfers its technology, leading to the commercialization of handheld LED devices.	Transition to portability. PBM moved from labs and clinics into portable, over-the-counter home formats for the first time.
$\sim 2010$	The FDA begins clearing LED PBM systems as Class II devices via the 510(k) pathway.	Regulatory parity. LED PBM systems were formally recognized under the same therapeutic regulatory framework as lasers, opening the US market.
$\sim 2015$	South Korean K-Beauty brands trigger an explosion of wearable LED masks.	Mass market lifestyle integration. PBM expanded from a clinical tool used for injury or illness into a daily cosmetic and skincare routine.
$\sim 2020$	Demand for home beauty devices surges during COVID-19, driving global sales of LED masks.	Mainstream adoption. Consumer PBM devices transitioned from a wellness niche into mainstream consumer electronics.
2020s	PBM systems integrate App and Bluetooth Low Energy (BLE) connectivity.	Data-driven PBM. The category shifted from simple timers to personalized dosing, data logging, and compliance tracking.

From Laser to LED: Democratization, Not a Downgrade

The historical trajectory of PBM from Mester’s focused laser beams to contemporary wearable LED masks is not a technical regression from premium to budget formats. Rather, it represents an engineering evolution from illuminating a single focal point to uniformly treating a broad surface area.

Whether the coherence (phase synchronization) and high monochromaticity (ultra-narrow spectral bandwidth) of lasers are mandatory for PBM remains a classic academic debate. However, accumulating clinical data has established a strong consensus: within the typical therapeutic dosing windows of PBM, coherence is not a prerequisite for biological efficacy.

Incoherent light from LEDs and coherent light from lasers produce equivalent biological outcomes under bio-equivalent conditions. The critical variables are wavelength, irradiance, energy density, and exposure duration—not the coherence of the source.

This realization shifted PBM from an intervention requiring clinical medical supervision to an automated consumer experience. The transition succeeded because high-density LED arrays made it possible to deliver large-area, uniform, and inherently safe PBM treatments at a cost accessible to the general consumer.

Unresolved Challenges: The Incomplete Science of PBM

Despite more than 50 years of published literature, several foundational questions within PBM science remain partially unanswered:

1. The Optimal Dose Remains Elusive: For most clinical indications, there is a lack of large-scale, dose-response RCTs to define the ultimate combination of wavelengths, irradiance, energy density, treatment frequency, and duration. Most contemporary protocols rely on parameters proven to be “effective,” which are not necessarily optimized.

2. High Inter-Individual Variability: Identical PBM parameters can produce significantly different responses across subjects. This variance is linked to individual differences in melanin content, tissue thickness, and localized blood flow, yet reliable protocols for personalized PBM prescriptions do not yet exist.

3. Pulse Width Modulation (PWM) vs. Continuous Wave (CW): Most home-use LED devices utilize PWM to generate pulsed light outputs. Evidence regarding whether pulsed light provides a distinct biological advantage over continuous wave illumination remains limited and inconsistent.

4. The Biphasic Black Box: The minimum effective threshold and maximum safe threshold vary by individual. A consumer device’s “standard program” might fall within the ineffective zone for some users while landing in the inhibitory zone for others, without any practical way for the end user to diagnose the discrepancy.

PBM FAQs

Q1: How does PBM differ from a hot compress? Doesn’t my red light mask feel warm?

This is a common misconception. Mester’s breakthrough in 1967 was specifically identifying a non-thermal effect. Under proper PBM dosing, the skin should not experience significant heat.

The mild warmth felt when using an LED mask or panel stems from two non-therapeutic sources: the operating heat of the LEDs themselves (which convert roughly 30–40% of electricity into light, dissipating the rest as heat) and the physical absorption of a fraction of the light by the skin. However, the core biological mechanism of PBM—photons targeting CCO to increase ATP—does not require thermal energy and triggers at irradiance levels well below the thermal threshold.

If a PBM device makes your skin feel hot, you may be receiving irradiance levels that exceed safe parameters, or the device suffers from poor thermal design that overheats the contact surface. The therapeutic vector of PBM is photons, not heat.

Q2: If my LED mask only emits 630nm red light, does it still provide a PBM effect?

Yes. The $630\text{ nm}$ wavelength is a widely documented PBM band that falls within the absorption spectrum of Cytochrome c Oxidase. CCO exhibits peak red absorption across the $620{-}670\text{ nm}$ band, and while the absolute peaks align closer to $660\text{ nm}$ (red) and $830\text{ nm}$ (NIR), adjacent wavelengths still achieve functional absorption.

The limitation of a standalone $630\text{ nm}$ source is its shallow penetration depth. It primarily acts upon the epidermis and superficial dermis. Its impact on deeper structural targets, such as deep dermal fibroblasts and underlying collagen networks, is weaker than that of NIR wavelengths ($830{-}850\text{ nm}$). A $630\text{ nm}$ single-band mask is effective for superficial photobiomodulation, but a dual-band Red + NIR combination is required to cover both superficial and deep tissue targets simultaneously.

Q3: Does PBM have side effects? Can I use it daily?

PBM presents a low risk profile when used correctly within low-to-moderate irradiance and energy density thresholds, though certain constraints apply:

• Ocular Protection: Prolonged, direct exposure to high-intensity LEDs can cause photochemical retinal damage. The risk stems from the high-intensity light source itself rather than PBM mechanisms, which is why compliant LED masks and panels integrate physical eye shields or opaque goggles.

• Photosensitizing Medications/Reactions: Individuals taking photosensitizing medications (such as certain antibiotics, retinoids, or St. John’s Wort) or diagnosed with photosensitive dermatological conditions (such as Lupus Erythematosus or Solar Urticaria) should seek clinical clearance before use.

• Melanin Interference: Darker skin phenotypes absorb more photons superficially, leaving less energy to reach deeper target cells under identical irradiance settings. While most consumer devices lack skin-tone matching dosing algorithms, the standard program might deliver an under-dosed treatment for darker skin profiles.

This document was authored by the RainbowDO Scientific Affairs Team to provide readers with a historical overview of Photobiomodulation (PBM) from its initial scientific discovery to its widespread consumer application. The scientific research cited represents findings reported in published literature; individual conclusions may be refined as new research emerges. Decisions regarding the selection and use of PBM equipment should combine personal requirements with professional medical guidance.