From published research and manufacturer specifications, not from a review unit on my desk. Where I have used something myself, the article says so. Links can earn a commission; the disclosure explains what that does and doesn't buy.
If you read nothing else
- The useful window is roughly 630 to 850nm. Outside it you're buying a different product.
- Dose is irradiance times time. Wattage on the box is not dose.
- Evidence is strongest for mild skin aging, moderate for joint pain, weak for recovery and hair.
- Cheap masks deliver a fraction of a panel's dose, and dose is the entire point.
- A seller who says FDA approved or promises to treat a disease has told you everything you need to know.
Red light therapy went from dermatology clinics to Amazon in about six years, and the marketing outpaced the evidence by roughly the same margin. It is not nonsense. It is also not what the listings claim.
The mechanism, in one paragraph
Photobiomodulation uses red and near-infrared light to influence mitochondrial function. The leading explanation is that specific wavelengths are absorbed by cytochrome c oxidase, which nudges ATP production and modulates oxidative stress and inflammation. This is a real photochemical effect, studied since the 1960s. It is also a modest effect with a narrow therapeutic window, which is the part marketing tends to leave out.
Wavelength
The usable window is roughly 630 to 850 nanometres. Red light at 630 to 660 penetrates shallowly and is most relevant for skin. Near-infrared at 810 to 850 penetrates several centimetres and reaches muscle and joint tissue.
A device that lists “red light” without a wavelength isn’t telling you what it does. A device at 590nm is a decorative lamp.
Dose
Measured in joules per square centimetre. Dose equals irradiance in milliwatts per square centimetre, multiplied by time in seconds, divided by a thousand.
This is where home users go wrong. The biphasic dose response means there’s a sweet spot: too little does nothing, too much can be less effective than the optimum. The effective range in most trials sits somewhere between 1 and 10 J/cm² at the tissue of interest, occasionally higher for deeper targets.
Two consequences. Irradiance falls off with the square of distance, so a panel rated 100 mW/cm² at six inches delivers roughly 25 at twelve. And wattage is electrical draw, not energy delivered to your tissue, so a 300W panel is not three times better than a 100W one.
Ask for irradiance at a stated distance, and the wavelength. If a seller can't give you both numbers, they're selling a light rather than a therapy. That single question filters out most of the category.
What the research supports
Best supported: mild to moderate skin aging and wound healing. Multiple trials show modest improvements in fine lines, texture and redness with consistent use over eight to twelve weeks. Real, small, and dependent on near-daily commitment.
Moderate: joint pain and stiffness. Trials in knee osteoarthritis and chronic neck pain show small to moderate short-term pain reductions. Effect sizes vary across studies and many trials are small.
Weak or mixed: muscle recovery and performance. Some studies show reduced soreness and better recovery markers, others show nothing. The heterogeneity is wide enough that claiming a clear benefit would be overreach.
Weak: hair growth. Some positive trials in androgenetic alopecia, mostly small, often industry-funded, with modest hair counts. Not a substitute for proven treatments.
Not supported: fat loss, detoxification, stem cell activation, testosterone, or any systemic effect from a tabletop device. Light doesn’t penetrate deeply enough to do most of what the marketing describes.
Panels, masks, wands
Panels deliver the highest irradiance over the largest area, which makes dose easy to reach. They cost $200 to $1,500, take floor space, and require standing in front of one for ten to twenty minutes.
Masks are convenient and dramatically underpowered. The LEDs sit on the skin, which helps, but the total energy delivered is usually a fraction of a panel’s. A $60 mask is a pleasant ritual with a small dose. A $400 mask is the same physics with better materials.
Wands are useful for a knee or wrist and impractical for anything larger, and they attract the most absurd medical claims of any product in this category.
Dose per dollar ranks panel, then wand, then mask. Adherence ranks the reverse. Adherence wins, because a protocol you skip has no effect.
Before you buy
Look for wavelengths listed individually, both red and near-infrared if you want tissue penetration. Irradiance at a stated distance. Treatment time to reach a stated dose, in the manual. Actual LED count and lens quality, because a 300-LED panel with no lens is mostly a heater. Cooling, since panels get hot and fans are necessary rather than a bonus. A warranty and a returns policy, because the failure rate on cheap panels is high.
And no disease claims. A seller claiming to treat arthritis, cancer or neuropathy is not a seller to trust with a medical device.
A defensible starting protocol
Six to twelve inches from the panel, consistent each session. Ten minutes per area, front and back if you’re treating something large. Four or five sessions a week for eight weeks before you judge it. Goggles on. Clean skin, no product, no sunburn.
Track something measurable, like a pain score or a photo in the same light at the same time of day. Memory is a poor instrument and this is exactly the category where people convince themselves of improvement they can’t demonstrate.
Who should skip it
Anyone treating a disease rather than a comfort or cosmetic goal. Anyone on photosensitising medication, without asking a clinician first. Anyone with a history of skin cancer in the treatment area. And anyone who won’t use it four times a week, because the protocol is the product.
General consumer information, not medical advice. If you're being treated for a skin condition, are photosensitive, or take photosensitising medication, ask a clinician before using any light device.
Common questions
Is red light therapy FDA approved?
No. Some devices are FDA-cleared as class II physical medicine devices for specific indications, which is not approval, and no device is approved to treat disease the way that phrase implies. Any seller saying FDA approved is confused or hoping you are.
How long until I see anything?
Skin studies typically run 8 to 12 weeks with near-daily use. Joint pain trials often use 2 to 4 weeks of treatment with effects measured shortly after. If a protocol asks for months of daily twenty-minute sessions, be honest about whether you'll do it.
Is more power better?
No, and this is where home users go wrong. Photobiomodulation has a biphasic dose response. Too little does nothing and too much can be less effective than the optimum. A 300W panel at six inches for twenty minutes is not automatically better than a 60W panel at six inches for ten.
Do I need eye protection?
For panels, yes. The light is bright and the long-term retinal effects of repeated high-irradiance exposure aren't well studied. Most panels ship with goggles. Wear them.
General information, not a diagnosis or a treatment plan. If pain is severe, came on suddenly, followed an injury, or hasn't improved in a few weeks, see a clinician. Full medical disclaimer.
Vefit Life