The Spectrum,
Indexed By Evidence.
Photobiomodulation — the study of how light changes biology — spans more than half a century of research. Below, the published science is organised the way REDelios reads light: wavelength by wavelength, from ultraviolet signalling to deep near-infrared energy.
Every Wavelength
Carries Its Own Evidence.
Select a wavelength to read its biological role, its tissue penetration, and the representative studies that have investigated it.
The surface 'glow' wavelength — red light absorbed in the upper skin, sitting near the ~620nm cytochrome-c-oxidase red peak and associated with tone, radiance and collagen support.
Deconvolved cytochrome-c-oxidase action spectra place a red absorption maximum near 620nm — the band 630nm sits on.
LabKaru & Kolyakov · Photomedicine and Laser Surgery · 2005
Polychromatic red/NIR raised intradermal collagen density and reduced fine lines in a controlled trial.
RCTWunsch & Matuschka · Photomedicine and Laser Surgery · 2014
Every Study,
Filterable By Wavelength.
150 graded studies, sorted by wavelength and strength of evidence. Filter by band or topic to narrow the library.
Identifies the human sulfotransferase forming the major sulfated vitamin-D metabolite — sulfation is real biochemistry.
Frequent tanners preferentially choose UV and report relaxation — behavioral reinforcement (β-endorphin not directly measured).
Cholesterol sulfate is the most abundant plasma sterol sulfate — a real membrane/keratinocyte-differentiation molecule.
25(OH)D3-3-sulfate is an abundant real circulating conjugate (~16.7 ng/mL) — the molecule is real (function as transport form unproven).
Chronic UV raises β-endorphin → naloxone-reversible opioid dependence in MICE; human extrapolation unproven.
NO significant rise in circulating β-endorphin after UV in humans (n=6) — a null human result; the human endorphin claim is thin.
"297 nm activates sulfation for bioelectric distribution" — no peer-reviewed mechanism, action spectrum or replication. Fringe.
UVB forms CPDs (and 6-4 photoproducts) → signature mutations in BCC, SCC, melanoma.
UV → cutaneous POMC/HPA → systemic and CNS endocrine signalling — the photohormonal axis.
NO/vasodilation is a UVA (315–400 nm) effect — NOT 297 nm UVB (band caveat).
Calcitriol/VDR regulates a large set of genes; broad genomic footprint of vitamin D.
Comprehensive account of the skin's UV-responsive neuroendocrine regulation of local/global homeostasis.
Solar UV (UVA/UVB/UVC) is Group 1 — carcinogenic to humans.
trans-UCA (stratum-corneum UV chromophore) → cis-UCA mediates UV photoimmunosuppression and photocarcinogenesis.
~2776 VDR binding sites near ~229 genes — the real basis for "vitamin D influences hundreds–1000+ genes" (not literally 2000).
UVB induces CD4+CD25+ Tregs and IL-10 — immunosuppressive and therapeutic, but reduces surveillance.
Authoritative review of vitamin-D physiology, skeletal and extra-skeletal roles.
UV→DNA damage→p53 drives keratinocyte POMC→α-MSH; p53-null mice cannot tan.
Standard vitamin-D action spectrum normalized to ~298 nm (adopted standard, under active revision).
Vitamin D/VDR pathway induces cathelicidin → kills intracellular pathogens — vitamin D as immune signal.
α-MSH→MC1R→cAMP→eumelanin; eumelanin photoprotective against UV damage and tumours.
Skin expresses the full HPA/POMC axis (CRH, POMC→ACTH/α-MSH/β-endorphin, cortisol) — a local neuroendocrine organ.
p53 drives apoptotic clearance of UV-damaged keratinocytes (sunburn cells); p53-mutant cells escape — apoptosis backstop + carcinogenesis.
58% of cutaneous SCCs carry UV-signature p53 mutations (C→T, CC→TT) — sunlight's molecular fingerprint in cancer.
In Boston (42°N) no vitamin D3 was synthesised in skin from November to February; in Edmonton (52°N) none from October to March — winter sun sits too low to make vitamin D.
Optimal previtamin-D3 production at 295–300 nm; ~65% 7-DHC conversion at 295 nm — the vitamin-D action-spectrum peak.
OPN5 mediates UVR-induced melanogenesis in human melanocytes via Ca2+/PKC — OPN5 photoreception in human skin.
Exposed skin contains OPN5-dependent local circadian photoentrainment — light-sensing skin clocks.
Continued UV degrades previtamin/vitamin D3 to inert photoproducts — UVA does NOT synthesize and can degrade vitamin D.
UVA penetrates deep dermis; UV→ROS→MMP-1 (collagenase)→collagen degradation→photoaging.
Ex vivo retina/cornea clocks photoentrain via OPN5, most sensitive to short wavelengths.
Endogenous porphyrins (Soret ~405 nm) and flavins absorb violet/UVA → ROS/singlet oxygen → antimicrobial effect.
Human and mouse OPN5 (neuropsin) absorb maximally at ~380 nm — the first human opsin with peak UV sensitivity, activating Gi.
UVA induces Nrf2 nuclear translocation and HO-1/antioxidant genes — protective antioxidant response.
UVA1 (340–400 nm) is an established phototherapy for morphea/scleroderma, atopic dermatitis, etc.
Placental mammals (incl. humans) lost photolyase — humans repair UV lesions by NER, not photoreactivation.
Optoacoustic penetration measurement: depth rises strongly with wavelength — UVA reaches the dermis, far deeper than UVB.
cis-UCA production peaks in UVB but extends through 305–341 nm — UVA contributes (relevant given sunlight's large UVA fluence).
UVA HO-1 induction is mediated by singlet oxygen via free heme — UVA→¹O2→gene activation (and an oxidizing carcinogen).
Melatonin-suppression action spectrum peaks ~464 nm (melanopsin) — far from 365 nm.
Independent melatonin-suppression peak ~459–464 nm — confirms blue, not UVA, suppresses melatonin.
Repetitive sublethal UVA generates the 4977-bp mtDNA "common deletion" via singlet oxygen — a molecular photoaging lesion.
Low-dose (20 J/cm²) UVA1 cleared >80% of morphea lesions (ultrasound/histology-confirmed).
UVA1 depletes skin T-helper cells by singlet-oxygen-driven FAS/FAS-L apoptosis — the actual mechanism of UVA1 phototherapy.
High-dose (130 J/cm²) UVA1 clears localized scleroderma dose-dependently, via MMP-1 (collagenase) induction.
UVA1 upregulates MMP-1 (collagenase) in morphea fibroblasts — the mechanism of UVA1's anti-fibrotic action.
High-dose UVA1 significantly improves atopic dermatitis vs UVA-UVB — foundational AD/UVA1 trial.
UVA (and H2O2/arsenite) induces HO-1 (HSP32) in skin fibroblasts — a general oxidant-stress defence.
Skin optics: longer wavelengths penetrate progressively deeper; UVA reaches the dermis (melanin/scattering-governed).
Long-wave UVA light prevents lens-defocus myopia in mice, dependent on retinal OPN5 — a direct OPN5/UVA clinical-adjacent mechanism.
Long-wave UVA light (360–400 nm) suppresses myopia progression in chicks and humans (implicates VL-opsin/OPN5/EGR1).
Long-wave UVA (~380 nm) light via hypothalamic preoptic OPN5 neurons suppresses brown-fat thermogenesis — deep-brain OPN5 physiology.
380 nm light via OPN5 drives a retinal dopamine pathway regulating ocular vascular development.
Most skin cell types have autonomous circadian clocks entrainable by central inputs and local cues.
Independently confirms OPN5 λmax ~380 nm; it is a bistable pigment (UV→blue 470 nm photoproduct, reverts) activating Gi.
OPN5 in CSF-contacting deep-brain neurons functions as a photoperiodic/seasonal photoreceptor — deep-brain UV photoreception.
UVA triggers labile-iron release that modulates NF-κB activation — a clean UVA→NF-κB inflammatory link.
Original identification/cloning of mammalian OPN5 (neuropsin) in neural tissue.
SCN-projecting RGCs are intrinsically photosensitive — the non-visual circadian photoreceptor system.
Melanopsin (OPN4, λmax ~480 nm) is the blue-light circadian photopigment — the longer-wavelength counterpoint to OPN5's UV sensing.
UVA → ROS → ERK1/2 phosphorylation → tyrosinase upregulation → melanogenesis (blocked by antioxidant).
Identifies OPN3 (encephalopsin), an extraretinal brain opsin — the broader non-visual opsin family context.
Timed bright light strongly phase-resets the human circadian pacemaker — light timing entrains the master clock.
Self-applied blue LED significantly reduced facial comedones over 8 weeks — a positive clinical signal (single-arm).
14 trials/698 participants: methodological limitations preclude firm conclusions — blue-light acne efficacy modest/uncertain.
OPN3 is the melanocyte sensor for short-wavelength visible light; Ca2+→CAMKII→CREB/MITF→tyrosinase → melanogenesis (persistent hyperpigmentation, esp. darker skin).
ROS mediate 405 nm cytotoxicity, with a differential dose response — bacteria far more sensitive than mammalian cells.
71 RCTs/4211 participants: high-quality evidence is lacking; blue-light acne efficacy is uncertain/modest.
A bactericidal 405 nm dose window exists below the mammalian-cell (osteoblast) damage threshold — selectivity.
Defines the blue-light hazard weighting B(λ), peak photochemical retinal sensitivity ~435–440 nm; 400–450 nm is the most hazardous visible band to the retina.
Continuous 405 nm disinfection reduced surface bacterial contamination 27–75% in occupied burns-unit rooms/clinics.
Ceiling 405 nm light continuously reduced surface staphylococci/MRSA by ~62% beyond standard cleaning — harmless to occupants.
Visible light induces more sustained, darker pigmentation than UVA1 in skin types IV–VI — the melasma/hyperpigmentation risk.
405 nm inactivates Gram-positive and Gram-negative pathogens without exogenous photosensitizer — via endogenous porphyrin excitation → ROS.
Reviews blue-light hazard, lipofuscin/A2E accumulation and its proposed role in age-related maculopathy.
C. acnes endogenous coproporphyrins photoexcited by high-intensity blue light → ROS → bactericidal; mechanistic basis of blue-light acne therapy.
The lipofuscin fluorophore A2E photosensitizes blue-light-induced apoptosis of RPE cells — the retinal-hazard mechanism.
Wearing blue-blocking glasses for 2 h before bed improved sleep onset, duration and quality versus clear lenses in adults with insomnia.
Amber blue-blocking lenses worn for 3 h before sleep improved subjective sleep quality and positive mood versus clear lenses in a randomized crossover trial.
18 RCTs/670 wounds: LLLT (modal 660 nm) significantly improved wound healing and reduced pain vs control.
RCT (136 subjects): polychromatic red/NIR increased intradermal collagen density and reduced fine lines (polychromatic, industry-adjacent).
660 nm LED raised type-I procollagen ~31% and lowered MMP-1 ~18%; clinically reduced wrinkles — direct 660 nm collagen evidence.
CCO-null cells still showed 660 nm proliferation enhancement — challenges the CCO-only mechanism (honest counterpoint).
670 nm reduces nanoscopic interfacial-water viscosity, proposed to ease ATP-synthase rotation — single-lab, speculative.
Penetration increases red→NIR; red (~660 nm) reaches a few mm, less than 810 nm NIR.
Red/NIR dissociates inhibitory NO from CuB of CCO → restored electron transport → ↑ATP/MMP; brief ROS signal.
PBM raises ROS in normal cells but lowers it in oxidatively stressed cells; biphasic; anti-inflammatory via NO/ATP/Ca2+.
660 nm raised ATP ≥24 h and increased COX protein; ATP-synthase inhibition abolished it — wavelength-specific ATP at 660 nm.
Comprehensive mechanism review: NO photodissociation, ATP, ROS/cAMP/Ca2+ signalling, membrane potential.
Consensus on PBM for oral mucositis — a well-evidenced clinical PBM indication with dosimetry/safety guidance.
Red/NIR PBM promotes fibroblast proliferation, collagen synthesis, ATP, NO release, wound healing.
RCT (44 men): 655 nm laser/LED helmet gave ~39% increase in hair count vs sham — androgenetic alopecia.
Red/NIR PBM improves muscle performance, delays fatigue and aids repair after exercise/injury.
Light (810 nm) generates intracellular ROS activating NF-κB and pro-survival genes — the ROS→transcription cascade (NIR study).
Reviews CCO as the red/IR-A photoacceptor and signal transducer (conceptual; exact peak numbers from Karu&Kolyakov 2005).
PBM is biphasic — an optimal dose stimulates, too much inhibits.
LLLT reduced acute and chronic neck pain (up to 22 weeks) vs placebo — the strongest-pedigree PBM analgesia evidence.
Red/NIR activates mitochondria→nucleus retrograde signaling via CCO, with ATP as a signaling molecule.
Deconvolved CCO action spectra: red maxima ~620 & ~680 nm (and NIR ~760 & ~825 nm); 660 nm is on the 680 nm shoulder.
CCO is the primary photoacceptor; lists NO release from CCO among primary mechanisms.
The founding LLLT paper — low-dose red laser accelerated wound/burn regeneration ("biostimulation").
Larger sham-controlled RCT confirming PBM acuity benefit in dry AMD (multiwavelength device).
ATP peaks in the morning; 670 nm raises ATP only when given ~08:00–11:00 — mechanistic basis for the timing effect.
A single 3-min MORNING 670 nm exposure improved colour contrast for ~a week; afternoon exposure did not — timing matters.
Multiwavelength (590/670/850 nm) PBM improved acuity/contrast and reduced drusen vs sham — multi-wavelength, not pure 670 nm.
Small human DME study — preliminary clinical PBM signal.
A single 15-min 670 nm exposure reduced post-OGTT glucose elevation ~28% AUC in healthy subjects — tiny, preliminary.
Longer wavelengths raise ATP/glucose demand while 420 nm suppresses — the spectrum/systemic-glucose mechanism (precursor to the 2024 study).
Brief 670 nm improves colour-contrast and rod thresholds in older humans — small n, surrogate endpoints.
Aged mice on 670 nm for 8 months lost <15% outer segments vs ~30% controls — structural retinal preservation.
670 nm improves aged retinal function, associated with corrected mitochondrial decline.
In-vivo NIRS: 670 nm (not 420 nm) progressively oxidizes CCO in aged retina for up to 2 h — direct in-vivo CCO readout.
670 nm in aged flies raised ATP, improved mobility and extended average lifespan — systemic aging effect.
670 nm restores oxidative-stress-suppressed phagocytosis in human RPE — a cell-level functional mechanism.
670 nm is absorbed by CCO and raises ATP/membrane potential in aged eyes, reducing pathology/inflammation.
670 nm upregulates cytochrome c oxidase and reduces inflammation in an age-related macular degeneration model.
670 nm raises mitochondrial membrane potential and reduces age-related retinal inflammation.
670 nm 3–4 min/day inhibits diabetic-retinopathy pathophysiology in vivo and in vitro.
670 nm pretreatment reduced lipid peroxidation and complement propagation in light-damaged retina — anti-inflammatory.
Foundational: 670 nm LED protects retina against a CCO inhibitor (formic acid) — 670 nm rescues the mitochondrial respiratory chain.
Tested 670/728/770/830/880 nm; 770 nm active; 830 & 670 nm most effective; effects parallel the CCO absorption spectrum.
Reviews transcranial PBM mechanisms and (early, heterogeneous) clinical evidence.
810 nm as a primary transcranial wavelength; reviews penetration and brain applications.
Open-protocol transcranial red/NIR LED improved cognition in mild TBI — small, uncontrolled.
Transcranial 633+870 nm LED improved cognition in chronic TBI — case reports (note: 870 nm, not 810).
810 nm acts via CCO; 980 nm via water-gated temperature/Ca2+ (TRPV1) channels — distinct mechanisms.
808 nm penetrates ~40 mm and has less absorption/scattering than both 660 and 940 nm — the deepest-penetrating tested.
Assigns the ~830–835 nm NIR band primarily to oxidized CuA — the molecular basis of 810 nm absorption.
The largest transcranial-laser trial — terminated early for FUTILITY, no benefit (honest negative).
A representative 940 nm PBM study — real but sparse/lower-impact; no robust replicated 940 nm efficacy base.
Argues bound water, not CCO, is the primary NIR acceptor — a contested minority hypothesis.
A 1267–1268 nm quantum-dot laser increased singlet-oxygen production in tumour cells — direct sensitizer-free ¹O2 generation.
Direct 1270 nm illumination killed cells via singlet oxygen with wavelength-specificity (1270 killed, 1247 nm control did not) — not thermal.
Confirms the direct ³O2→¹O2 absorption bands (765 nm b¹Σ and the ~1270 nm a¹Δ) — the physics of sensitizer-free singlet-oxygen generation.
Pulsed (40/100 Hz) produced distinct cognitive effects vs CW in 56 adults — pulse rate matters, but no clean frequency→effect map.
Pulsed 810 nm at 40 Hz changed resting EEG power in a pilot (small, no comparator frequencies, device-affiliated author).
40 Hz multisensory gamma entrainment is neuroprotective in mice — distinct sensory-network mechanism.
40 Hz light+sound improved pathology/cognition in AD mice — sensory gamma, mouse-dominant; human evidence early/mixed.
Coherence/laser not required — LEDs give equivalent PBM at matched wavelength and power density.
Describes the pronounced biphasic dose response and NO/ROS/ATP secondary cascade.
40 Hz VISUAL FLICKER entrains gamma oscillations and reduces amyloid/modifies microglia in AD mice — sensory, not tissue-PBM, mechanism.
10 Hz pulsed 810 nm was most effective vs CW and 100 Hz in mouse TBI — a specific pulse rate can outperform CW (single rodent study).
Reaffirms biphasic response; documents reciprocity failure — irradiance is an independent determinant, not just total fluence.
Pulsed light is sometimes superior to CW for some conditions; evidence mixed; optimal pulse parameters NOT established (some authors industry-affiliated).
Each absorbed photon activates at most one molecule in the primary photochemical act.
Photochemical effect ∝ intensity × time (total dose) — with biological reciprocity-failure limits.
Only radiation absorbed by a system can produce photochemical change — spectrum must match a chromophore.
Light attenuates exponentially with path length and absorber concentration.
Irradiance from a point source ∝ 1/distance².
— Delta 0.5–4, theta 4–8, alpha 8–12, beta 13–30, gamma 30–100 Hz; 100 Hz is high/fast gamma, not high-beta.
The Names
The Literature Keeps Returning To.
Across thousands of papers, the same handful of researchers keeps appearing in the citations. This is the work the field is built on.
Author of the foundational reviews on how red and near-infrared light act on mitochondria and the cell.
Key work — anti-inflammatory mechanisms of photobiomodulation (2017)
Identified cytochrome c oxidase as the key photoacceptor for red and near-infrared light in cells.
Key work — primary mechanisms of red/NIR light on cells (1999)
Research on near-infrared light, mitochondrial function and ageing vision in later life.
Key work — 670 nm light improves aged human vision (2020)
Led NASA-funded research using LED light for wound healing and tissue repair.
Key work — NASA LED light for wound healing (2001)
Mapped how the timing of light sets the circadian clock that governs sleep, energy and metabolism.
Key work — circadian timing of light & metabolism
Showed that sunlight releases nitric oxide stored in the skin, supporting circulation and blood pressure.
Key work — UVA, nitric oxide & blood pressure (2014)
Clinical research into photobiomodulation and laser therapy protocols across medicine and dentistry.
Key work — photobiomodulation therapy reviews
Clinical photobiology and the measurement (dosimetry) of therapeutic light in medicine.
Key work — clinical photobiology & light dosimetry
Identified the active form of vitamin D and how UVB sunlight produces it in human skin.
Key work — vitamin D, sunlight & human health (2007)
Research on the skin's own response to light — melatonin, vitamin D metabolism and stress signalling.
Key work — skin neuroendocrinology & photoprotection
Listed for their published contributions to the science of light. Affiliations reflect notable positions in their work; inclusion here does not imply any endorsement of REDLIGHT.DOCTOR or its products.
Light,
By Nobel Prize.
The biology of light isn't fringe — it has been recognised by the Nobel committee for more than a century.
Light as medicine. Recognised for treating disease with concentrated light — the first Nobel for therapeutic light (phototherapy).
Light into life. Mapped how light energy is captured and fixed into the chemistry of living things (photosynthesis).
How the eye reads light. The physiology and chemistry of vision — how photoreceptors turn light into a biological signal.
The clock that light sets. The molecular mechanism of the circadian rhythm — the body's daily clock, entrained by light.
The Research Pointed One Way.
We Built The Device.
REDelios ONE translates the full biological spectrum — UV, visible red and near-infrared — into a single engineered system.