Red light therapy—often discussed under photobiomodulation (PBM)—typically uses red and near-infrared (NIR) light sources, most commonly LEDs. The important factor is not simply that a lamp looks red, but that it delivers defined wavelengths at an appropriate irradiance and dose.

Common Wavelengths Used

Different devices use different wavelengths and combinations. Common examples include:

There isn't one universally "best" wavelength for every purpose. Device design, irradiance, treatment time, distance and intended application all matter.

1. Red LEDs

Visible red LEDs, particularly around 630–660 nm, are widely used.

A 660 nm deep-red LED is especially common because it falls within a frequently used PBM wavelength region and is readily available in high-output LED packages.

Red light primarily interacts with relatively superficial tissues compared with longer-wavelength near-infrared light.

Common device formats include facial masks, handheld devices, therapy panels and flexible LED pads.

2. Near-Infrared LEDs

Near-infrared LEDs emit wavelengths longer than visible red light.

Common examples are:

810 nm / 830 nm / 850 nm

NIR is invisible or only weakly perceptible to human vision, so an 850 nm LED can be operating even though it does not appear nearly as bright as a 660 nm red LED.

NIR is commonly incorporated when a device is intended to deliver light deeper into tissue than visible red alone.

3. Red + Near-Infrared Combination

Many modern PBM panels combine visible red and near-infrared LEDs.

A common configuration is:

660 nm Red + 850 nm NIR

More sophisticated devices may use several wavelengths, for example:

630 + 660 + 810 + 830 + 850 nm

This allows the device to provide a broader combination of visible-red and NIR radiation rather than relying on one wavelength.

4. LEDs vs. Lasers

Both LEDs and low-power lasers can be used in photobiomodulation applications, but they are not interchangeable devices.

LEDs are particularly suitable for illuminating relatively large areas. They can be arranged into panels, masks or flexible arrays containing dozens or hundreds of emitters.

Lasers produce more directional and coherent light and may be used in specialized or clinical equipment.

For large-area consumer PBM devices, LED technology is particularly common.

5. What Types of LED Packages Are Used?

Red-light therapy equipment can use different LED packages depending on required optical power, thermal management, viewing angle and device construction.

Possible packages include:

2835 SMD LED – Suitable for dense LED arrays and relatively uniform illumination.

3030 SMD LED – Offers a useful balance between package size and output.

3535 SMD LED – Frequently suited to higher-power red and infrared applications.

Other high-power or specialized packages can also be used.

The package itself doesn't determine whether an LED is appropriate for PBM. Its wavelength and optical characteristics are more important.

For example:

3535 660 nm → Deep-red LED

3535 850 nm → Near-infrared LED

The same physical package can therefore contain very different semiconductor dies.

Ordinary Red Bulb vs. Therapy LED

This is why an ordinary red household bulb should not automatically be considered a red-light therapy device.

Irradiance Is Also Important

Wavelength is only one part of the specification.

A PBM device also needs an appropriate irradiance, typically expressed as:

mW/cm²

This describes the optical power delivered over a particular area.

Treatment dose is commonly expressed as:

J/cm²

A device could use 660 nm LEDs but still deliver a very different dose depending on LED output, optics, distance and exposure time.

Therefore:

Wavelength + Irradiance + Time = much more useful information than color alone.

Why Are 660 nm and 850 nm So Common?

The 660 nm + 850 nm combination has become common in commercial LED panels because it combines a visible deep-red wavelength with a near-infrared wavelength.

The 660 nm LEDs provide visible red illumination, while 850 nm LEDs extend the device's output into the NIR region.

However, this does not mean these two wavelengths are automatically optimal for every medical or wellness application.

What Should LED Device Manufacturers Consider?

For manufacturers sourcing LEDs for PBM equipment, simply ordering a "red LED" or "IR LED" is not sufficiently specific.

A component specification should consider:

Wavelength: e.g., 660 ± 5 nm or 850 ± 10 nm

Radiant flux: optical output of the LED

Radiant intensity: particularly relevant when beam direction matters

Viewing angle: affects treatment-area uniformity

Forward voltage/current: required for driver design

Thermal resistance: important for maintaining output and wavelength stability

Wavelength tolerance: helps maintain consistency between production batches

For a complete therapy panel, engineers should additionally evaluate irradiance at the specified treatment distance, uniformity, dose, thermal management and applicable photobiological/electrical safety requirements.

The most common lights used in red light therapy are red LEDs and near-infrared LEDs. Common wavelength regions include 630–660 nm for visible red and 810–850 nm for near-infrared, with 660 nm + 850 nm being a common combination in LED panels.

SMD packages such as 2835, 3030 and 3535 can potentially be used to build these systems, provided they offer the required wavelength and optical performance.

Most importantly, red appearance alone does not make a light suitable for red light therapy. The wavelength, irradiance, dose, treatment distance, thermal performance and safety of the complete device all need to be considered.