Older walker watching a master mason and apprentices repair a hole in a cobbled road by red lantern light.
Back to the library

Recovery

Red light and wound healing

Light therapy added to standard wound care has been tested mainly in diabetic foot ulcers, where a meta-analysis of seven randomised trials reported higher odds of complete healing and greater reduction in ulcer area. A dermatology review of randomised LED trials also placed acute wound healing among the better-supported uses. This is hospital and podiatry work, delivered under professional supervision, not something to manage with a panel at home. Anyone with an open wound or an ulcer should be under the care of a clinical team and should ask them before using light over it.

Evidence so far
Moderate
Reading timeAbout 12 minutes

Start here

Why this is being studied

Wound healing here means the repair of broken skin, from a surgical incision to a long-standing diabetic foot ulcer. Red light at around 630 to 660 nm is absorbed within the first few millimetres of tissue, which is exactly where the repairing cells sit, and the same near-infrared wavelengths used elsewhere reach a little deeper. The proposal is that light absorbed by mitochondria in fibroblasts and keratinocytes may support the energy production, migration and growth factor signalling that repair depends on.

Where the evidence stands

Flag text

The mechanism

What is going on, and why this might help

What is going on in a healing wound

Repair runs through overlapping phases: bleeding stops, inflammatory cells clear debris and bacteria, fibroblasts lay down new collagen, keratinocytes migrate across the gap to close the surface, and new small blood vessels grow in to supply it. In a wound that is not healing, usually because of diabetes, poor circulation or persistent infection, the process stalls in the inflammatory phase with cells that are still alive but energetically and metabolically struggling.

What the light is absorbed by

Cytochrome c oxidase in the mitochondria of fibroblasts, keratinocytes and immune cells absorbs red and near-infrared light. Where nitric oxide is bound to that enzyme and slowing respiration, the model is that absorbed photons displace it, lifting oxygen use and ATP output. The nitric oxide released locally relaxes small vessels and increases blood flow, which matters in a tissue whose problem is often supply. A low-level burst of reactive oxygen species acts as a signal, activating transcription factors that increase growth factor expression, collagen synthesis and cell migration, and shifting inflammatory cells towards resolution rather than persistence.

The biphasic dose response

Fragile, thin or broken tissue is where over-dosing is most plausible as a real risk, because there is no intact epidermis to attenuate the light. The published curve has no effect below a threshold, a working window, then a decline and possible inhibition above it. Wound trials generally use low single-figure doses delivered frequently, which is the opposite of the intuition that a worse wound needs more light.

How far the light actually goes

Red light reaches a few millimetres, which covers the epidermis, dermis and the base of a shallow ulcer, and near-infrared reaches further into subcutaneous tissue. This is the favourable case for light: the target is the surface. It is also the case where self-management is least appropriate. An open wound, a diabetic foot ulcer or a recent surgical site should be assessed and dressed by a clinical team, and members should ask that team before using any light over it.

Explainer illustration

The studies

Every study is laid out the same way: what the researchers wanted to find out, who took part, what they actually did, what they found, why it might work and where the limits are. No jargon, and a link to the original if you want to read it yourself.

Each study is laid out the same way: what the researchers asked, who took part, what they did, what they found, why it might work, and where the limits are. The clinician layer at the end of each one carries the numbers.

Paper 1

Efficacy of low-level light therapy for treatment of diabetic foot ulcer: a systematic review and meta-analysis of randomized controlled trials

Li et al. · Diabetes Research and Clinical Practice · 2018 · Systematic review and meta-analysis of seven randomised controlled trials, n=194

Read the paper

What they asked

Diabetic foot ulcers heal slowly, recur often and can lead to amputation, and standard care of dressings, offloading and infection control does not always work. Small trials had suggested light therapy might help as an addition to that care, but they were scattered and inconsistent. This Chinese group asked whether, pooled together, randomised trials show that adding low-level light to standard care increases the chance of complete healing and shrinks ulcer area faster.

Who took part

Seven randomised controlled trials covering 194 adults with diabetic foot ulcers were pooled. These were people under clinical care with established, often long-standing ulcers, rather than healthy volunteers with a graze. All trials compared standard ulcer care plus light against standard care plus a placebo or standard care alone.

What they did

The reviewers searched the medical databases, assessed the quality of each trial, and pooled two main outcomes: the proportion of ulcers that healed completely, and the change in ulcer area over the study period. They also recorded adverse events. Devices and doses varied between trials, which the reviewers described rather than ignored.

What they found

The pooled analysis reported substantially higher odds of complete healing with added light therapy, with an odds ratio of about 6.7, and a greater reduction in ulcer area compared with the control groups. No serious adverse effects attributable to the light were reported across the included trials.

What it means

An odds ratio of that size is striking, and it is consistent with the laboratory picture of light supporting the cells that rebuild skin. It is also the kind of number that should prompt caution rather than enthusiasm, because very large effects from very small pooled samples often shrink when larger trials arrive. The practical reading is that this is a promising addition to professional wound care, delivered in a clinical setting alongside everything else that care involves.

Limits

One hundred and ninety-four people across seven trials is a small base for a confident conclusion, and small trials tend to produce inflated effect estimates. The trials used different devices, wavelengths and doses, so no single protocol is supported. Blinding in wound trials is difficult and outcome assessment can be subjective unless standardised photography is used. Most importantly, every trial delivered light as part of supervised clinical care, with the dressings, debridement and offloading that go with it.

Paper 2

Light-emitting diodes in dermatology: a systematic review of randomized controlled trials

Jagdeo et al. · Lasers in Surgery and Medicine · 2018 · Systematic review of 31 randomised controlled trials

Read the paper

What they asked

LED devices had spread through dermatology and the consumer market faster than the evidence behind them. This review asked a clarifying question: across all randomised controlled trials of LED light in skin conditions, which uses are actually supported, which are not, and how good is the underlying research.

Who took part

Thirty-one randomised controlled trials were included, covering people with a range of skin conditions including acne, herpes lesions, wounds, psoriasis and signs of skin ageing. Sample sizes in individual trials were typically small, often a few dozen people, and the trials came from a variety of countries and settings.

What they did

The reviewers searched systematically for randomised trials specifically using LED rather than laser devices, extracted the condition treated, the wavelength, dose and schedule, and the outcomes reported. They then judged the strength of evidence for each indication and described the recurring methodological problems across the field.

What they found

The review gave its strongest grades to acne, herpes lesions and acute wound healing. Evidence for other uses was weaker and in several cases inconsistent. Across the whole set, the reviewers highlighted small samples, widely varying and often poorly reported light parameters, and short follow-up as the field's persistent weaknesses.

What it means

Placing acute wound healing among the better-supported LED uses is meaningful, because it comes from a review that was willing to be unimpressed by most of what it read. It also supports a general principle worth repeating: red light does best where the light does not have to travel far and the target tissue is thin and accessible.

Limits

A systematic review can only report what has been studied, and dermatology LED trials are mostly small. Grades assigned across conditions are a summary judgement rather than a precise measurement. Inconsistent reporting of irradiance and dose means that even well-graded indications do not come with a protocol that transfers reliably from one device to another.

Paper 3

Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring

Avci et al. · Seminars in Cutaneous Medicine and Surgery · 2013 · Narrative review of mechanisms and clinical uses in skin

Read the paper

What they asked

This review set out to gather what was known about how light affects skin at the cellular level and to connect that biology to the clinical uses being proposed. Rather than testing a treatment, it asked what the light is doing to fibroblasts, keratinocytes and immune cells, and which of the claimed applications that biology can reasonably support.

Who took part

This is a review of laboratory, animal and human work rather than a study with participants of its own. The evidence it draws on ranges from cell cultures and mouse wound models to small human trials, and the authors are careful to distinguish between them, which is why it remains a standard reference rather than a promotional piece.

What they did

The authors assembled the cell biology of light absorption in skin, covering cytochrome c oxidase, nitric oxide, reactive oxygen species signalling and the transcription factors switched on downstream, and then mapped that onto wound healing, scarring, ageing, hair and inflammatory skin conditions. They also discussed dose, wavelength and the biphasic response.

What they found

The review describes a consistent laboratory picture: light at appropriate doses is reported to increase fibroblast proliferation and collagen production, support keratinocyte migration across a wound, modulate inflammatory signalling and increase growth factor release. It also states plainly that the human clinical evidence is patchier than the cell biology, and that dose is the recurring problem.

What it means

This is the mechanistic backbone for the wound healing work. It explains why the clinical trials point the way they do, and it is honest that a coherent mechanism is not the same as a proven treatment. For members it is the clearest statement of what the light is thought to be doing to skin cells.

Limits

A narrative review is not systematic, so the authors chose what to include. Much of the underlying material is cell culture and animal work, where doses can be controlled precisely in ways that are impossible through living skin. Laboratory findings about fibroblasts do not establish that a session in front of a panel changes how a wound heals in a person.