Red light therapy: the dose is the difference

What the light actually does

Red light (roughly 620 to 700 nm) and near-infrared light (700 nm and up) pass into the body in a way other light does not. The standard explanation is that an enzyme inside your mitochondria, cytochrome c oxidase, absorbs it. That shifts how much energy the cell makes, releases a short burst of signalling molecules, and changes calcium levels inside the cell.¹

It is a tidy explanation. It is also incomplete. Cells engineered to have no cytochrome c oxidase at all still grew faster under 660 nm light.² Something else is going on.

Two other explanations are worth knowing.

Most people know melatonin as the sleep hormone released at night. A large share of sunlight arrives as near-infrared.⁵ The melatonin idea is still a hypothesis. But it reframes sunlight as something your cells use directly, not only a signal to your body clock.

Why depth matters

Different wavelengths stop at different depths. Red at 630 and 660 nm is mostly absorbed in the skin. Near-infrared at 810 and 850 nm travels further, into muscle and around joints.

• For skin: red.
• For deeper tissue: near-infrared.
• For general use: both together, which is why most serious devices combine them.

The part almost everyone gets wrong

Light follows a curve. Too little does nothing. The right amount helps. Beyond that, the benefit flattens and then reverses.⁶ The same signalling molecules that help at low levels cause damage at high ones.

Dose is measured in joules per square centimetre (J/cm²). It depends on two things: how strong the light is at your skin (irradiance, in mW/cm²) and how long you stay there.

Most home protocols aim for roughly 20 to 30 J/cm² per area.

The catch is that the irradiance printed on the box is rarely what reaches you. Most manufacturers measure with solar power meters, which read roughly double what a calibrated spectrometer shows. Independent spectrometer tests of five popular panels found every one 33 to 57 percent below its advertised figure.⁷

Distance matters just as much. Light falls off with the square of the distance. Sit at 12 inches instead of 6 and you lose roughly three quarters of the dose.

What the research supports

Sunlight, fire, and the light you already have

At sunrise and sunset, the low angle of the sun filters out much of the blue and UV, leaving light weighted toward red and near-infrared. Firelight, candles, and incandescent bulbs give off a similar warm spectrum. For almost all of human history, that was the light people lived under.

Modern LED lighting is heavy in blue with almost no red. Jeffery's group suggests a day spent entirely under it may be a quiet public health problem.¹³

Be realistic about scale. Measured midday sun delivers around 15 to 21 mW/cm² of red and near-infrared, depending on the season. That adds up over time outdoors, but it is lower than a panel at 6 inches. Sunlight is the foundation. A device concentrates the dose.

Three changes that cost nothing:

• Get outside in the first hour of daylight, even for ten minutes.
• In the evening, use warm incandescent or halogen bulbs where you can, or the warmest LEDs you can find.
• Choose firelight or candlelight over overhead light at night.

The two devices I would choose

These are affiliate links. If you buy through them, Self Care Sunday earns a small commission at no extra cost to you. I chose them against the research first.

Hooga ULTRA750 panel

Why this one. Every LED carries four wavelengths: 630 and 660 nm red, 810 and 850 nm near-infrared. That covers skin and deeper tissue in one session. Red and near-infrared brightness adjust separately from 1 to 100 percent, which is exactly what good dosing needs: start low and build. It is flicker-free, Hooga states 0.0 μT EMF at 6 inches, and it ships with goggles, a door mount, and a 3-year warranty.

The honest note. Hooga lists more than 161 mW/cm² at 6 inches. I have not found an independent spectrometer test of this model. Given how other panels test, I plan sessions on roughly half that figure.

How to use it

• Distance: 6 inches for deeper tissue. Further back for the face and general use, allowing for the drop in dose.
• Time: 4 to 6 minutes per area at 6 inches. That lands around 20 to 30 J/cm² at about 80 mW/cm².
• Frequency: four or five shorter sessions a week beat one or two long ones.
• Mode: continuous. Pulse mode at a 50 percent duty cycle delivers half the energy in the same time. Research on recovery points to total dose and wavelength as what matters, not pulsing.¹⁴ Some animal work favours 10 Hz for healing,¹⁵ which is interesting, not proven.
• Goggles on, every time.

See the Hooga ULTRA750 on Amazon

CurrentBody Series 2 face mask

Why this one. 236 LEDs at three wavelengths: 633 nm, 830 nm, and 1072 nm. The first two are the pair used in the published wrinkle trials. The flexible silicone sits close to the face, which keeps the dose consistent from one session to the next. It is FDA cleared.

The honest note on 1072 nm. It reaches deeper into the skin, but the evidence is thinner. One placebo-controlled trial of 79 people found 32 percent better skin texture after 8 to 10 weeks, by the participants' own assessment.¹⁶ Earlier 1072 nm trials, on cold sores, were run by a researcher with a financial stake in the technology. Two proven wavelengths, plus one promising one.

How to use it

• Follow the built-in 10-minute cycle, 3 to 5 times a week.
• Eyes closed under the mask.
• Use it on clean, dry skin. Apply retinol or acids afterward, not before.
• Give collagen changes 8 to 12 weeks.

See the CurrentBody Series 2 on Amazon

A simple way to use it

1. Morning

   Ten minutes outside in early light. On panel days, near-infrared on whatever is sore or stiff.

2. Evening

   Mask or red light on the face. Sit through the session with the Pranayama Reset breath. Then warm, low light for the rest of the night.

Before you switch it on