Not all red light is the same. Two devices that both glow red can differ greatly – in effect as well as in price. When both are switched on, these differences are often invisible. What matters are components that are barely visible when you buy: the lenses, the driver and the cooling.
This page explains the seven factors that actually determine the effect. For each factor you will also find a question you can use to check it yourself – for any supplier, including us.
If you are comparing right now and are short of time, this is the summary. The reasoning behind each row follows on the next pages.
| Factor | What matters | Market standard | heilys® |
|---|---|---|---|
| 01Wavelengths | The right ones, not the most | 2 (660 + 850 nm) | 6, selected according to the CCO curve, body of studies and penetration depth · tolerance ± 5 nm |
| 02Control | Precisely adjustable and easy to use | hard-wired, one switch | each wavelength individually dimmable · 6 presets + 12 custom · touch display, app and one-button remote control |
| 03Irradiance | Within the effective window, not at the maximum | Figure given without distance or measurement method | 82 mW/cm² at 15 cm (spectrometer) · 182 (Solarmeter) — both published |
| 04Dosage | Adjustable, because too much achieves as little as too little | fixed output | continuously dimmable, timer, time and distance specified for each application |
| 05Homogeneity | No hotspots, even illumination | one type of lens for everything | Gen panels: two lenses, 60° red / 30° NIR · FaceMask 2.0: closer LED spacing |
| 06Light quality | Genuinely flicker-free, low EMF, pulsing only where harmless | “flicker-free” with no details on the technology | DC driver → 0 Hz · EMF at ambient levels · pulsing on NIR only |
| 07Verification | Independently tested, not self-declared | Own claims | German Institute for Product Testing: grade 1.1 · CE, RoHS, WEEE · 5-year guarantee |
The light output of a panel is limited. The more wavelengths are used, the more the available output is spread across those wavelengths.
So the right question is not “how many?” but “by what criteria were they selected?” Three criteria are decisive:
The absorption curve of cytochrome c oxidase has peaks and troughs. 830 nm sits at a peak. Placing light on a weak part of the curve costs energy without delivering a comparable return.
There is a reason why 660 nm appears in more than 400 studies, while neighbouring wavelengths have been studied in only a fraction of that number. Weak evidence makes the data sheet longer, but does not automatically make the result better.
Red light reaches about 1-3 mm, near-infrared about 3-7 mm. A device that covers only one of these two depths can accordingly reach only one type of application.
Red light works through absorption, not heat. Between 600 and 900 nm – the therapeutic window – light reaches the enzyme cytochrome c oxidase in the mitochondria, where it increases ATP production.
Outside this range, less of use happens: short-wave light is scattered more strongly in the top few millimetres. Infrared above 1000 nm is absorbed by water and mainly produces heat.
Most panels use 660 and 850 nm. The reason is simple: these LED types were originally mass-produced for plant lighting and are therefore inexpensive. This is the obvious choice, but not automatically the best-founded one.
heilys® uses six wavelengths with a manufacturing tolerance of ± 5 nm. Together they cover around 82 % of the CCO absorption curve (Tran et al., 2024).
Six is not a number chosen just because it sounds good. It is the result of the three filters mentioned.
| Wavelength | Depth | Studies | Why it is included |
|---|---|---|---|
| 630 nm | 1–3 mm | 200+ | Skin, collagen formation, anti-inflammatory effects |
| 660 nm | 1–3 mm | 400+ | the most extensively studied wavelength of all |
| 670 nm | 1–3 mm | 150+ | ATP production, retina, neuroprotection |
| 810 nm | 3–7 mm | 300+ | deep tissue, muscles, brain |
| 830 nm | 3–7 mm | 250+ | Peak of CCO activation |
| 850 nm | 3–7 mm | 180+ | Tendons, joints, immune modulation |
Two requirements meet here that can easily get in each other’s way. Nevertheless, both have to be met.
Photobiomodulation is a young field of research. A device with a fixed factory setting reflects the state of research in the year it was produced – and stays at that level permanently.
Then there is the individual factor: skin type, build, age, goal and tolerance all differ. Only if settings can be readjusted and saved can you find out what works for your own use.
This is where many technically good devices fail. If you first have to go through three menu levels to start a session, it will quickly be skipped after a long working day.
Red light is used regularly over a period of weeks. The user interface does not determine the effect of the light itself, but it very much determines whether the device is used regularly at all.
Standard panels are often hard-wired: one switch, everything on. At the other end of the spectrum are devices with such overloaded apps that in the end only a single mode gets used anyway.
For precision: each of the six wavelengths is individually dimmable. In addition, there are 6 well-founded presets, 12 freely configurable programmes and lifelong software updates.
For everyday use: touch display, app and a remote control with a quick-start button. One press is all it takes to start the most recently saved setting.
Full control when you need it – and one button when you don’t.
The test question: How many steps do I need to start my usual session? If it is more than one, ask yourself: will I really do this every day?
Light acts in the cell via a signal. When light hits cytochrome c oxidase, a small and controlled amount of reactive oxygen species (ROS) is briefly produced. It is precisely this signal that triggers the adaptation: more ATP, better cellular respiration and regeneration.
If the intensity is too high, the cell produces more ROS than its antioxidant systems can neutralise. The signal turns into oxidative stress. Instead of ramping up, the cell then switches into a protective mode. Excess energy can do harm where regeneration was actually meant to be supported. Excessive intensity can therefore reverse the desired effect.
| Application | Sensible irradiance |
|---|---|
| Skin, anti-ageing, supporting wound healing | 20–50 mW/cm² |
| Muscles, joints, deep tissue | 70–100 mW/cm² |
| Target range for an all-round device | 40–100 mW/cm² |
| over 100 mW/cm² | no proven additional benefit, but excess ROS and heat |
For context: the midday sun delivers around 100 mW/cm² in total. Of this, about 20-30 mW/cm² lies within the therapeutic window. A device advertised at 200 mW/cm² therefore delivers many times what nature provides in this range.
Both values have been measured correctly. However, only one of them is meaningful for the therapeutic effect!
This does not mean, however, that a weak device is sufficient. Irradiance decreases significantly as the distance increases. A panel that still reaches 30 mW/cm² at 15 cm delivers only a fraction of that output at 50 cm. That is why output and treatment distance must always be considered together.
Power in reserve makes sense – but only if you can also reduce the intensity. A high maximum output is of little use if it cannot be adapted to the application.
We measure with a spectrometer, state the distance and also publish the Solarmeter value. This lets you compare our figure with other suppliers, even though it makes our number look smaller.
The 82 mW/cm² is not a compromise on the low side but a deliberate choice: enough reserve for different distances without unnecessarily overtaxing the cells.
Irradiance describes how fast energy arrives. The dose, on the other hand, describes how much energy arrives in total.
The cells receive light, but the amount remains below the threshold at which enzyme activity changes measurably. The effect is then not simply weaker – it may not occur at all.
This is a common reason why people give up after a few weeks: too great a distance, sessions that are too short or a device that is too weak.
The same mechanism is at work here as with excessive intensity, only over time: the ROS signal can tip over into oxidative stress. The cell then scales down instead of up.
Simply doubling the time therefore does not automatically produce a greater effect – in the worst case, it may even produce less.
The effective range lies between a dose that is too low and one that is too high. Whether the dose is outside this range usually cannot be felt or seen directly during the session.
That is why time and distance are not just non-binding recommendations but part of the application.
Getting started: in the first week, 2-3 min per area every other day. Then increase to 3-5 sessions per week, with a maximum of 20 min per area.
| Goal | Dose | Distance | Duration |
|---|---|---|---|
| Skin, anti-ageing | 3–15 J/cm² | 45–60 cm | approx. 8 min |
| Joint discomfort | 10–40 J/cm² | 15–30 cm | approx. 10 min |
| Muscle recovery | 20–50 J/cm² | 15–30 cm | approx. 12 min |
| Energy and vitality | 10–30 J/cm² | 30–60 cm | approx. 10 min |
| Wound healing support | 10–40 J/cm² | 15 cm | approx. 7 min |
| Sleep and recovery | 3–15 J/cm² | 30–45 cm | approx. 7 min |
| Eyes (670 nm) | 3–15 J/cm² | 30 cm | 1–5 min, in the morning |
Irradiance decreases as distance increases. The times and distances given should therefore be considered together. The 82 mW/cm² of the Gen300 refers to a measuring distance of 15 cm.
A panel consists of many individual LEDs. If the light is not distributed evenly, one area of skin receives considerably more energy than the one next to it. Then not every area receives the same dose – and the calculation from factor 04 no longer applies to the entire surface.
Two optics: 60° for the red wavelengths (630/660/670 nm) and 30° for the near-infrared wavelengths (810/830/850 nm).
In the Gen300, 306 LEDs are arranged so that the light cones of both optics overlap. Red and infrared light reach the same area of skin at the same time – without gaps or hotspots.
The dual-lens design is not an extra, but the prerequisite for six wavelengths to work together effectively.
A different lever is used here. Because the mask sits directly on the face, the distance between the individual LEDs has been reduced.
More closely spaced points of light produce significantly more even illumination at short distances.
The goal remains the same: in the end, every area of the skin should receive the same dose.
Three properties all depend on the same component – the power supply – and yet hardly appear on any data sheet.
Flicker is a visual effect: the brightness of the light fluctuates, usually in time with the mains frequency. Above a certain frequency, you no longer perceive it consciously. The visual system still registers the fluctuation, however. Sensitive people may react to it with restlessness, eye strain or headaches.
The term “flicker-free” is used very loosely. Many manufacturers simply mean that the frequency is so high that the flicker lies above the threshold of conscious perception.
But invisible flicker is still flicker. A higher frequency does not eliminate the fluctuation in brightness; it merely hides it. Genuine freedom from flicker is only possible with a DC driver. This supplies the LEDs constantly instead of switching them on and off in cycles. The result is 0 Hz – not just a low value, but no flicker frequency at all.
The decisive question is therefore not just “Is it flicker-free?”, because almost everyone answers yes to that. It is: “Does the device run on direct current, and what is the flicker frequency in hertz?”
Pulsing is deliberately generated flicker. The LEDs are switched at a fixed frequency, usually between 10 and 50 Hz.
There is visible light that pulses at 10 to 50 Hz. This is precisely the frequency range that can trigger seizures in photosensitive people. With a large panel that takes up a large part of the field of vision, this is not a purely theoretical risk. Pulsed visible red light therefore has no place in a panel.
The situation is different with small devices that sit directly on a specific area of the skin: there, the light source is on the skin and not in the field of vision.
Whether electromagnetic fields are produced is not the decisive question – every power supply produces them. What matters is how much the device adds to the electromagnetic fields already present in the environment.
Every power supply generates an electromagnetic field. During red light sessions you often sit 15 to 60 cm away from the device – and frequently every day.
We expressly do not derive any health claim from this. For us, a different benchmark makes sense.
Every living space already has an electromagnetic background level from the household wiring, appliances and power supplies.
A well-designed red light device should not significantly raise this existing level. This is technically feasible. And what is feasible should also be implemented.
heilys® Gen panels work with DC drivers. The flicker frequency is 0 Hz.
Pulsing is only possible in the NIR spectrum and can be selected in the app between 10 and 50 Hz. Near-infrared is invisible, so there is no risk of photosensitive reactions from visible pulsed light. The visible red wavelengths in the panel always run continuously – deliberately and without exception.
As for EMF, our values at the point of use are at the level of the normal background level of a home environment. The device therefore adds practically nothing to its surroundings.
LEDs lose light output when they get too hot. They also age faster. Your dose calculation may then be correct in the first minute, but no longer later on.
Passive: silent and less expensive, but limited in the amount of heat it can dissipate. This makes sense for small devices.
Active: technically more complex and not completely silent, but keeps the output stable. Above a certain power class, active cooling is practically the only option – a 480-watt panel cannot be cooled passively in any sensible way.
We use active cooling where the output requires it: in all Gen panels and FullBody panels as well as in the Gen30 and Gen50. The smaller devices manage with passive cooling.
The fans run quietly: approx. 36 dB at 15 cm and approx. 33 dB at 50 cm – roughly in the range of a whisper.
100,000 hours LED lifespan · 5-year guarantee · 30-day right of return · CE, RoHS, WEEE DE 19301058 · developed and tested in Germany.
Independently tested
The heilys® Gen300 was rated 1.1 by the German Institute for Product Testing (Deutsches Institut für Produkttests). View the test report →
Wavelengths: Which wavelengths are included – and why were exactly these chosen?
Control: How precisely can the device be adapted to my use?
Irradiance: What is the output at a realistic distance, and how was it measured?
Dosage: Does the manufacturer give specific recommendations on intensity, distance and session duration?
Homogeneity: How does the device ensure that the surface is evenly illuminated?
Light quality: Is the visible light really flicker-free, and how are pulsing and EMF addressed technically?
Cooling/verification: Does the output remain stable during the session, and have the specifications been verifiably tested?
We answer all seven questions on this page. If another supplier can do the same – excellent. That is exactly the point: you should not simply take our word for it, but be able to compare the devices yourself.
Depending on the application, our devices differ in treatment area, design and features. What matters most, therefore, is which part of the body you want to illuminate at once and whether you are looking for a solution for at home, on the go or for targeted use.
Red light does not suppress melatonin production – unlike blue light. You can read what this means for your evening under Sleep & recovery. Learn more →
