Photobiomodulation, the umbrella term for therapeutic red and near-infrared light, is delivered in two quite different ways. Large LED arrays and beds treat broad areas at relatively low intensity. Laser probes deliver concentrated light to a small, specific point.
They are not competing versions of the same thing, and the choice between them is mostly determined by what you are treating and how deep it sits.
What is photobiomodulation therapy?
Photobiomodulation therapy, often shortened to PBM, is the use of red and near-infrared light at low intensity to influence how cells function. Light at these wavelengths is absorbed inside the cell, chiefly by the mitochondria, and the leading explanation is that this supports cellular energy production and moderates inflammation and oxidative stress in the treated tissue.
The important word is low. Photobiomodulation does not cut, burn or heat tissue to produce its effect. It is the term now preferred in the research literature, and it covers both of the delivery methods compared in this article.
Low level laser therapy and cold laser therapy: are they the same?
Yes. Low level laser therapy, usually abbreviated to LLLT, and cold laser therapy are older names for photobiomodulation delivered with a laser. "Cold" simply means the laser does not heat tissue, in contrast to the surgical lasers used to cut or ablate.
Photobiomodulation replaced both terms because "low level" was never clearly defined and because LEDs, which are not lasers, produce comparable effects at the right dose. If a clinic advertises LLLT, cold laser or PBM laser treatment, it is describing the same category of treatment. What distinguishes one provider from another is the device, the dose and the clinical reasoning, not the label.
The difference between LED and laser
Both deliver light at therapeutic wavelengths. The difference is in how that light behaves.
LEDs emit light that spreads as it travels and covers a wide area. Power is distributed across that area, so intensity at any one point is comparatively low. This suits treating large regions.
Lasers emit coherent, collimated light: the waves stay in step and the beam stays tight rather than spreading. That concentrates energy into a small area, allowing more to be delivered to a specific point, and generally achieving greater depth.
A useful analogy is a floodlight versus a torch beam. Both illuminate. One covers the garden, the other reaches the end of it.
Why depth matters
Light does not penetrate tissue uniformly. Different wavelengths reach different depths, and the amount of light reaching a given depth falls off sharply.
Red light is absorbed relatively superficially, which is why it is discussed in relation to skin. Near-infrared penetrates further, which is why it is used for deeper tissue.
This is the practical crux. A superficial target can be reached by a broad LED array. A deeper structure, such as a joint, generally requires the concentration a laser provides. Treating a deep target with a device that cannot reach it means the tissue you care about receives very little.
Where each fits
Full-body LED systems
Best suited to treating large areas at once: general recovery after training, widespread muscular soreness, or where the objective is broad coverage rather than one specific point.
The practical advantage is coverage and consistency. In a full-body system the distance between the LEDs and your skin is fixed by the design, so the dose is controlled rather than estimated. Sessions are short and passive.
Laser probes
Best suited to a specific, localised target, particularly a deeper one. A clinician places the probe directly over the structure being treated and delivers a defined dose to that point.
Treatment is hands-on and targeted, and typically forms part of a wider treatment session rather than standing alone.
Using both
Where a person has both a specific local problem and a broader recovery need, the two are complementary. A laser addresses the particular structure; a full-body session addresses general recovery. Neither substitutes for the other.
LED light therapy: face masks, panels and beds
LED light therapy is a broad label. It covers at least three quite different kinds of device.
- LED face masks and handheld devices. Low-powered, designed for the skin of the face, and used mainly for cosmetic goals such as skin tone and mild acne. They treat a small, superficial area.
- LED panels. Flat arrays used at home or in clinics for a region of the body. Output varies enormously between products, and the dose depends on how far you stand from the panel.
- Full-body LED beds. Clinical systems such as the NovoTHOR surround the body with a large array of LEDs at a fixed distance, delivering a controlled whole-body dose in a single short session.
All three use LEDs, but they are not interchangeable. A face mask will not do the job of a bed, and a bed is not the tool for treating one small patch of skin. Our guide to red light therapy beds explains how full-body treatment differs from panels.
Laser therapy for pain: class 3B and class 4 lasers
Lasers are classified by output power, and two classes are used for pain and tissue repair.
Class 3B lasers have an output of up to 500 milliwatts. They are the devices on which most low level laser therapy research was carried out, and they produce no meaningful heating. Low level laser probes of the kind used for photobiomodulation, including THOR probes, are typically in this class.
Class 4 lasers exceed 500 milliwatts and are sometimes marketed as high-intensity or high-power laser therapy. They deliver a dose faster and produce noticeable warmth, which means the operator has to keep the beam moving to avoid overheating the skin.
Higher power is not automatically better. Because photobiomodulation follows the dose-response curve described below, what matters is the total dose reaching the target tissue, not the class printed on the device. The conditions with the most supportive evidence for laser therapy are tendon problems, neck pain, osteoarthritis-related joint pain and some soft tissue injuries, with effects that are generally modest and build over a course of sessions.
Dose is the thing that determines whether it works
The most consequential principle in photobiomodulation, and the most frequently ignored.
Effects appear to follow a biphasic dose-response. There is a range in which effects are observed, and exceeding it does not increase the effect and may reduce it. Too little does nothing. Too much can be counterproductive.
This is why professional practice specifies wavelength, power, treatment area, distance and duration, rather than simply treating for as long as feels reasonable.
It also explains a common experience with consumer devices. A device whose real output is far below its advertised figure delivers a dose below the effective range, and the user concludes that photobiomodulation does not work, when what actually happened is that they never received a therapeutic dose.
On the size of the evidence base
Photobiomodulation has been studied extensively. The research literature across low-level laser therapy and photobiomodulation runs to thousands of published papers spanning laboratory work, animal studies and clinical trials.
Two honest caveats about that literature.
First, quantity is not quality. It includes a great deal of small, methodologically limited work alongside better-designed trials.
Second, and more practically: because dose parameters vary so widely between studies, results are genuinely inconsistent, and much of that inconsistency is thought to reflect differences in dose rather than the treatment failing outright. Studies delivering doses outside the effective range would not be expected to show an effect.
The applications with the more established evidence include aspects of tissue repair and certain musculoskeletal pain presentations. Photobiomodulation is also used in some oncology settings, under specialist supervision, to manage side effects of cancer treatment.
Where you should be sceptical is the broad wellness marketing, which frequently cites the overall size of the literature as though it constituted proof for whatever specific claim is being made.
Red light therapy at home: how home devices compare
Home red light therapy devices have improved, and for some uses they are a reasonable choice. The main differences from clinical equipment are these:
- Output. Independent testing has found that some consumer panels deliver well below their advertised irradiance. Look for third-party measurements rather than the figure on the box.
- Dose control. With a panel, the dose changes with every few centimetres of distance. Clinical beds fix the distance, and laser probes are applied in contact with the skin.
- Coverage and depth. A small panel or mask treats a small superficial area. It cannot replicate a full-body session or reach a deep joint the way a laser probe can.
- Guidance. A home device comes with generic instructions. A clinic sets wavelength, dose and frequency for the problem being treated, and changes them if you are not responding.
A sensible approach is to use a clinic to establish whether photobiomodulation helps your particular problem, then decide whether a home device is worth buying for maintenance. The safety points below apply at home as well, particularly eye protection and photosensitising medication.
Questions worth asking any provider
- What wavelengths does your device use?
- What is the irradiance, and at what distance was it measured?
- What dose does your protocol deliver, and why that dose?
- Is the device certified, and for what?
- Do you have both broad-area and targeted options, and how do you decide?
A provider who can answer these understands what they are doing. One who answers only with claims about benefits does not.
Safety
Red and near-infrared light is non-ionising and does not carry the DNA-damaging risk associated with ultraviolet light. Neither LED nor laser photobiomodulation is comparable to a sunbed.
Laser devices carry specific eye-safety requirements, and appropriate protective eyewear should be used with both. Contraindications include photosensitising medication, active cancer, photosensitive conditions and pregnancy. Our guide to red light therapy safety covers these in detail.
Frequently asked questions
Is laser stronger than LED?
More concentrated rather than simply stronger. It delivers more energy to a small area and generally reaches deeper. For treating a large area, that concentration is not an advantage.
Is it hot?
Therapeutic photobiomodulation operates at low intensity and is not primarily a heating treatment. Mild warmth is common. This is different from high-power surgical lasers, which are an entirely different category.
How many sessions?
Effects are generally cumulative rather than immediate, so a course is typical. A single session is not a fair test.
Can I get the same result at home?
For a small superficial area, a good home device used correctly may be reasonable. For depth, for large areas, or where dose accuracy matters, clinic equipment differs substantially.
Does it hurt?
No. Most people feel nothing, or mild warmth.
Photobiomodulation in Chiswick
We offer full-body red light therapy using a NOVOTHOR system and targeted laser treatment using THOR probes at Omnia Lifestyle in Chiswick, W4, close to Turnham Green station, on bus routes 94, E3 and 272. Limited parking is available on request when booking. Having both means we can match the delivery method to what is actually being treated rather than applying one approach to everything.
Learn more about red light therapy, or book a consultation.
This article is general information, not medical advice. If you have a medical condition or take regular medication, discuss photobiomodulation with your doctor first.
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