Last updated: July 2026 · Written by the Dermfix phototherapy team
Short answer: In a controlled lab study on human endothelial cells (the cells that line blood vessels and drive wound healing), red and green LED light both significantly boosted cell proliferation and migration, while blue light did not — and even appeared to work against these processes at the cellular level. If wound healing and circulation support are the goal, red and green wavelengths currently have the stronger evidence behind them.
The study
A team from the Ludwig Boltzmann Institute for Experimental and Clinical Traumatology in Vienna, led by Sabrina Rohringer and Peter Dungel, set out to directly compare how different LED wavelengths affect human umbilical vein endothelial cells (HUVEC) — the standard lab model for studying blood vessel formation (angiogenesis). The team tested pulsed LED light at three wavelengths: 475nm (blue), 516nm (green) and 635nm (red), against untreated control cells. The full study was published in Scientific Reports (Nature) in 2017.
Endothelial cells matter here because they line the inner walls of blood vessels and are directly responsible for forming new capillary networks at sites of tissue damage — a process central to how wounds heal.
What red and green light did
After 72 hours, both red and green light significantly increased how many endothelial cells were present compared to untreated controls — cell counts were roughly 144–146% higher in the red and green groups. Blue light, by contrast, produced only a modest increase that didn't reach statistical significance.
The pattern held up across multiple types of testing. In a standard “scratch wound” assay — where a gap is created in a layer of cells and researchers track how quickly it closes — green light produced the fastest, statistically significant closure. In a 3D model designed to mimic how cells migrate through tissue, both red and green light significantly increased the number of cells migrating outward, while blue light showed no effect at all.
The researchers also looked at early-stage vessel formation in a 3D co-culture model combining endothelial cells with stem cells. Both red and green light increased the area occupied by proliferating cells and caused visible cell elongation — a sign of cells actively working to form new connections with each other.
What blue light did
Blue light stood out for the opposite reason. It significantly reduced cell metabolic activity relative to control, was the only wavelength to trigger a significant rise in reactive oxygen species (ROS) — which, at excess levels, can be damaging to cells — and consistently failed to improve migration or proliferation in any of the in vitro assays.
The authors do note an important nuance: other studies from the same lab have found blue light can be effective in live animal models, particularly for releasing nitric oxide from mitochondrial proteins in ways that support healing. The take-away isn't that blue light never works — it's that in this direct, cell-level comparison, red and green consistently outperformed it.
So why do multi-wavelength panels still include blue?
It's a fair question to ask of a study like this — including of our own hardware, since the Dermfix RLF range includes 480nm among its seven selectable wavelengths. Three things are worth separating out.
First, this was an in vitro study on endothelial cells, testing each wavelength in isolation for a vascular outcome. It is not a test of a multi-wavelength panel, and it does not measure the applications blue light is normally selected for in skincare contexts.
Second, the same research group has separately shown blue light producing benefits in living animals through a different mechanism — nitric oxide release — which a petri dish cannot reproduce. The authors themselves flag this.
Third, and most practically: on a selectable-wavelength panel, blue is one option among several rather than the whole treatment. If your goal is circulation, wound healing or tissue repair, this study is a good argument for selecting the red and near-infrared wavelengths rather than blue — which is exactly the point of independent wavelength control.
We publish research like this even where it complicates the marketing story, because a wavelength you can switch off is only useful if you know when to switch it on.
Why green light is the interesting finding
Red light's benefits for tissue repair are well established in the LLLT literature. What makes this study notable is that green light performed just as well — and on some measures (2D migration), slightly better. The mechanism isn't fully worked out yet; the authors point out that red light is generally understood to act through cytochrome c oxidase in the mitochondrial respiratory chain, but green light's pathway “has to be further elucidated.” At the protein level, the study found that both red and green light stimulation increased levels of hepatocyte growth factor (HGF), a pro-angiogenic signal, though the specific proteins affected differed somewhat by wavelength.
What this means practically
Wavelength combination: For applications centred on skin repair, circulation, and tissue regeneration, this study adds direct cell-level support for red-light devices, and suggests green light may deserve more attention than it currently gets in most consumer panels, which rarely include it.
Not a substitute for in vivo evidence: The authors are careful to flag that this is an in vitro (cell-culture) study — real wound healing in a living body involves oxygen gradients, ischemia, and enzyme activity that a petri dish can't replicate, which is likely why blue light behaves differently in animal studies than it did here.
Frequently asked questions
Does this mean blue light is useless?
Not necessarily. This study found it ineffective and mildly counterproductive at the cell level, but the same research group has shown blue light can help wound healing in live animal models, likely through a different mechanism (nitric oxide release) than red or green light.
Is green light better than red light?
They performed similarly overall, with green edging out red on 2D migration speed specifically. The study treats them as comparably effective rather than declaring an outright winner.
What wavelengths were actually tested?
475nm (blue), 516nm (green), and 635nm (red), all delivered as pulsed LED light at a peak irradiance of 80 mW/cm² and a daily dose of 24 J/cm².
Is this study specific to skin, or all tissue?
It used endothelial cells specifically — the cells that form blood vessels — rather than skin cells directly. Since new blood vessel formation underlies most wound-healing and tissue-regeneration processes, the findings are relevant to skin healing but were not tested on skin cells themselves.
Sourced from: Rohringer, S., Holnthoner, W., Chaudary, S., Slezak, P., Priglinger, E., Strassl, M., Pill, K., Mühleder, S., Redl, H. & Dungel, P. “The impact of wavelengths of LED light-therapy on endothelial cells.” Scientific Reports 7, 10700 (2017). DOI: 10.1038/s41598-017-11061-y. Published under a Creative Commons Attribution 4.0 International License.
Disclaimer: this article summarises published research for general information. It is not medical advice and does not describe the intended purpose of any Dermfix product.