Red light therapy, explained: 660 and 850 nanometres

Red light therapy is ten minutes in front of panels that shine two specific colours of light on your skin: 660 nanometre red, which you can see, and 850 nanometre near-infrared, which you cannot. The panels are not hot, they do not tan you and they carry no UV. The scientific name is photobiomodulation. This article explains what that word means, why those two numbers, and what you can honestly expect.

Photobiomodulation in plain words

Photo means light. Bio means living tissue. Modulation means a nudge, not a blow. Put together: light that gives cells a small push. The leading explanation is that red and near-infrared light is absorbed by an enzyme inside the mitochondria, the parts of your cells that make energy. Researchers such as Michael Hamblin describe this as a chain of small signals: a little more cell energy, a brief burst of signalling molecules, and changes in how cells behave over the following hours. That is the mechanism as proposed in the lab. How much of it shows up as a benefit you can feel is a separate question, and we get to it below.

Why 660 and 850 nanometres

Light is measured by wavelength. Not every wavelength gets into tissue. Blue and green light are absorbed at the surface. Far-infrared mostly turns into heat. Between roughly 600 and 900 nanometres sits what scientists call the optical window: the range where skin and water absorb little, so light travels deepest and reaches the enzyme mentioned above.

• 660 nm red is absorbed close to the surface. It is the wavelength most studied for skin.
• 850 nm near-infrared penetrates a few centimetres further. It is invisible, which is why the panels look dimmer than they are. It is the wavelength most used in studies on muscle and joints.

Most research panels and most clinical devices use one or both of these. Freezlab uses both at once so one session covers the whole range.

What the panels do and do not do

Three things people often assume, and all three are wrong.

• No heat. These are LEDs, not infrared heaters. You may feel slightly warm because you are standing still in a quiet room, not because the light is cooking you.
• No UV. Ultraviolet sits below 400 nanometres. Red light is far above that. Nothing in the panel damages DNA the way sun or a sunbed does.
• No tan. Your skin colour does not change. If you want a tan, that is a different service with different considerations, and we have written about it separately in the journal.

What the panels do is deliver a measured dose of light. Dose is the whole game. Too little and nothing happens. Too much and studies show the effect flattens or reverses, which is one reason home devices and clinic devices give different results.

How a ten minute session goes

1. You undress to the level you are comfortable with. Light only works on skin it reaches, so shorts or underwear give the best coverage.
2. You stand or sit at the distance the panel is set for. Distance matters as much as time.
3. You put on the goggles. Red light at this intensity is not dangerous to eyes, but it is bright and the goggles make it easy to relax.
4. Ten minutes. Most members use it as quiet time. Phone away, breathe.
5. Done. No downtime, no redness, nothing to wash off.

The session costs 2 credits, or €15 as a single.

What the research actually looks like

The research base is large and uneven. There are thousands of papers on photobiomodulation. Many are lab or animal studies. Among the human trials, most are small, many use different devices and doses, and a good number lack a proper placebo group. That makes big claims hard to support, and dismissal equally lazy.

Where the evidence sits today, honestly graded:

• Skin. Some evidence, and the best-studied area. Controlled trials show measurable changes in skin texture and collagen density with regular use over weeks.
• Muscle recovery and soreness after exercise. Early evidence. Small trials suggest a modest effect, mostly when light is applied before training. Results vary a lot.
• Joint and tendon pain. Some evidence, mostly with lasers rather than panels, and doses differ.
• Mood, sleep, energy. People report benefits. The trial evidence is thin here.

A fair summary: the mechanism is plausible, the safety record is good, and the size of the benefit depends on what you are hoping for and how consistently you show up.

Honest expectations

You will not feel much during a session. Some people feel calmer afterwards, which may be the light or may be ten minutes of doing nothing. Skin changes take weeks of regular sessions, not one visit. If you try it for a month and notice nothing, that is useful information too. It is safe to combine with everything else at Freezlab.

How it fits into a week at Freezlab

Most members pair red light with something else. A common pattern is three minutes of cryotherapy, then ten minutes under the panels to warm up and wind down. Two or three sessions a week is a realistic rhythm for anyone with a job and a family. Read the full details on the Red Light Therapy page, or book a session. New to Freezlab? The Trial Membership gives you enough credits to test it properly for a month.

Freezlab does not diagnose, treat or cure medical conditions. If you are unsure whether a therapy suits you, talk to your doctor.