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Is Red Light Therapy Safe to Use?
I wanted to clarify something about red light, in regards to what I learned recently from Dr Jack Kruse. So I wanted to write this up to share but also some new perspectives.
Is Red Light Therapy Safe to Use?
Here's What Actually Matters
This is one of the most common questions in our community. People see a red light panel and immediately wonder if it's doing something harmful. Is it disrupting hormones. Is it messing with sleep. Is it safe to use every day.
Short answer: yes, it's safe. Long answer: the real question isn't "is red light safe," it's "when and why are you using it."
Summer Rule: Get Outside First
Right now it's summer. The sun is up early, setting late, and full-spectrum sunlight is sitting right outside your door for free.
If you have access to real sunlight, that always wins over a panel. Sunlight isn't just red and near-infrared. It carries the full spectrum your mitochondria evolved to use, along with UV that drives vitamin D production, nitric oxide release, and skin health in ways no panel replicates.
Red light panels exist to fill the gap when the sun isn't available. In winter, at high latitudes, or if you're stuck inside all day, that's when a panel earns its keep. In summer, your first move should be outside, barefoot if you can, skin exposed, before you reach for a device.
Why Red Light at Night Doesn't Blunt Melatonin
Here's the part that confuses most people. They think any bright light at night is a melatonin killer. That's true for white light, blue light, and most LED lighting. It is not true for red light.
Melatonin suppression isn't about how bright a light is. It's about wavelength. Your eyes have a specific receptor, melanopsin, sitting in the retinal ganglion cells. Melanopsin is tuned almost exclusively to blue-green wavelengths, in the 460 to 490 nanometer range. That's the signal your brain reads as "it's daytime, hold off on melatonin."
Red and near-infrared light sit way outside that range, typically 630 to 850 nanometers. Melanopsin barely responds to it. So even if a red light panel is pumping out a high lux reading, one of those old-school light meters, your brain's melatonin machinery doesn't register it as daytime. You can use red light in the evening, even at what looks like high intensity, and your circadian signaling stays intact.
It’s never just about brightness. It's about the frequency of light hitting your retina and your skin, and what your mitochondria do with that specific information.
Standard “lux” is a photometric measurement. It’s weighted to how the human eye perceives brightness overall, which peaks in the green-yellow range. It has nothing to do with melatonin.
Melatonin suppression is driven by melanopsin, and melanopsin only responds to a narrow blue-green band, roughly 460-490nm. A red light panel can read “high lux” on a standard meter and still barely activate melanopsin at all, because almost none of its output falls in that band.
• Bright blue-white light = high lux AND high melanopic stimulus = melatonin drops
• Bright red/near-infrared light = can also read high lux, but low melanopic stimulus = melatonin stays intact
Jack argues (correctly) that lux is the wrong metric to judge melatonin impact by, since it doesn’t isolate the wavelength your eye actually uses for that signal.
🔔 But I will say based on clinical experience, and with myself, there are some people who are very sensitive to using red light. If they use it in the morning or at night it can impact sleep. I don’t think it’s a melatonin issue but more a boost in ATP. So just go slow if you find you are that person.
The Mitochondrial Piece
There's a deeper reason red and near-infrared light behave differently in your body. Cytochrome c oxidase, an enzyme sitting in your mitochondria, absorbs light strongly in the red and near-infrared range. When it absorbs that light, it can boost electron transport and ATP production. This is the mechanism behind red light's effects on skin repair, inflammation, and recovery.
Blue light doesn't do this. Blue light drives cortisol and alertness signaling through the eyes. Red light drives energy production at the cellular level. Different wavelength, different job.
The Bottom Line
Red light therapy is safe to use, day or night. The two things that actually matter:
- In summer, prioritize real sunlight over a panel whenever you can get outside
- At night, red and near-infrared light won't blunt melatonin the way white or blue light will, regardless of how bright it looks on a meter
Your body isn't asking "is this bright." It's asking "what color is this light, and what time of day does that color mean."
Red light, at any hour, tells your body the same thing: repair mode, not daytime.
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Is Red Light Therapy Safe to Use?
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