Red light therapy has real evidence behind it — and a *lot* of hype bolted on top. The difference usually comes down to four things. Learn these and you can tell in about 30 seconds whether a study (or a product claim) means anything.
The scientific name for all of this is **photobiomodulation (PBM)**, sometimes **low-level light/laser therapy (LLLT)**. Studies use LEDs *or* lasers — both count.
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## 1. Wavelength (which nm?)
Light only does something if the tissue can absorb it, and that depends entirely on the **wavelength**, measured in nanometres (nm).
- **~630–660 nm (visible red)** — absorbed near the skin's surface → skin, complexion, superficial tissue.
- **~415 nm (blue)** — different job again (e.g. acne bacteria).
A study that says *"we used 660 nm and 850 nm at X dose"* is doing it right. A product or article that just says *"red LED light"* with **no wavelength** is a red flag — you literally can't tell what it was doing.
👉 Takeaway: **no wavelength stated = ignore the claim.**
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## 2. Dose — this is where most people (and most marketing) go wrong
Two numbers, and you need both:
- **Irradiance** = how *intense* the light is where it hits you, in **mW/cm²** (milliwatts per square centimetre).
- **Dose** = irradiance × time, in **J/cm²** (joules per square centimetre). This is the actual "amount" of light delivered.
Simple version: **mW/cm² × seconds ÷ 1000 = J/cm².** A panel at 100 mW/cm² for 100 seconds delivers 10 J/cm².
Three things this tells you:
- **Distance matters enormously.** Irradiance drops fast as you move away from the panel. A number measured *touching* the device (0 cm) looks huge and means nothing for real use. Always look for the distance a figure was measured at (e.g. "at 15 cm").
- **More is not better — there's a sweet spot.** PBM follows a *biphasic* dose response: too little light does nothing, the right dose helps, and *too much* can actually do less. This is why "3000W, 1200 LEDs!!" marketing misses the point.
- **Beware inflated intensity numbers.** A "solar meter" reading is inflated and fine only for rough comparison; a **spectrometer**-measured figure at a stated distance is the honest one.
👉 Takeaway: a real study reports **wavelength + irradiance (mW/cm²) + dose (J/cm²) + distance/time.** If those are missing, the product/panel/mask can't reproduce it and neither can you.
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## 3. What *kind* of study is it? (the evidence)
Not all "studies" are equal. Strongest to weakest:
**Systematic review / meta-analysis** of human trials — pools many studies. Strongest.
**Randomised controlled trial (RCT)** in humans — people randomly assigned, ideally with a sham/placebo group and blinding.
**Cohort / observational** human study — useful, but can't prove cause.
**Animal study** — mechanism only; mice ≠ humans.
**In-vitro (cells in a dish)** — shows *how* it might work, not that it actually works in a person.
A headline like *"red light boosts collagen!"* that traces back to **cells in a dish** is not the same as an Random Controlled Trial on actual faces. Both are legitimate science — they just answer very different questions. Say which one you're citing please........and we all love photos of course :-)
Ideally also glance at: **sample size** (10 people vs 200), whether there was a **control/placebo group**, whether it was **blinded**, and any **conflict of interest** (who funded it - that's quite enlightening sometimes).
👉 Takeaway: **"an RCT found…" ≠ "a lab-dish study suggests…".** Always label the level.
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## 4. Quick red-flag checklist
Before you trust a red light claim, ask:
- ❓ Does it state the **wavelength(s)** in nm? (No → bin it.)
- ❓ Does it give **dose** (J/cm²) or at least **irradiance at a stated distance**?
- ❓ Is it a **human study**, or is a dish/animal result being stretched to humans?
- ❓ **Sample size** — a handful of people, or a proper trial?
- ❓ Was there a **placebo/sham** group?
- ❓ Who **funded** it, and is that disclosed?
- ❓ Is the claim about the **exact condition** studied, or a leap ("helped wound healing" → "cures everything")?
If most of those check out, it's worth taking seriously. If they don't, it's probably marketing.
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**When you post a study here**, try to include: the wavelength(s), the dose, the study type, and one honest line on its limitations. That one habit is what makes this sub better than a Google search.
*Not medical advice. Discuss, disagree, and bring sources.*
# Red Light / Photobiomodulation — Master Evidence List
A running index of the research on red and near-infrared light therapy (photobiomodulation / PBM), sorted by topic. **Bookmark it. Add to it.** If you have a study that belongs here, drop it in the comments with the link and we'll add it.
**How to read the tags** (be honest about strength — that's the whole point of this sub):
- 🟢 **Strong** — multiple human studies / systematic reviews
- 🟡 **Moderate** — human studies, but fewer or smaller
- 🟠 **Emerging / mixed** — early human data, promising but not settled
- 🔴 **Early / frontier** — mostly reviews, animal or very preliminary. Interesting, not proof. Be sceptical.
- ⚪ **Safety / context**
*Not medical advice. Photobiomodulation (PBM / LLLT) is the scientific umbrella term; studies use LED or laser, and wavelength + dose matter a lot — see the “How to read a red light study” post.*
*Note: this list is about red / near-infrared light. UVB phototherapy and vitamin D are a different topic (different wavelengths) and aren't included here.*
*Got a study to add — or think one of these is over-rated? Comment below with the link and your reasoning.*
Short answer: wound-healing is one of the oldest, best-supported uses. Studies in diabetic wounds show wavelength-dependent effects (red light significantly outperformed controls), and reviews of pressure injuries report promising healing and lesion-size reduction.
Discussion: Anyone had red light applied for this reason in hospital or clinic settings? (I have seen used on TV in dermatology settings)
Short answer: small studies of combined 830 nm + 633 nm LED phototherapy reported high clearance and satisfaction in recalcitrant psoriasis, with a pain-free, side-effect-free profile. Early-stage evidence — encouraging, not conclusive, and we need more trials please. I think UVB has the much stronger effect from my experience over 20 years.
Discussion: anyone used red/NIR alongside or instead of conventional psoriasis care?
Short answer: blue light (~415 nm) targets acne-causing bacteria; combining it with red light has shown improvements in inflammatory lesions in controlled studies. It’s a possible supporting tool, not a replacement for proven acne treatments. Must admit I am quite a fan of blue light for the antibacterial side of things.
Discussion: red-only, blue-only, or combined — what did people find, and any irritation?
Short answer: Photobiomodulation does have a real body of evidence for pain, including knee osteoarthritis and general musculoskeletal pain. A comprehensive review calls it “effective and non-invasive” for arthritis, though optimal parameters are still being pinned down. I am a bit on the fence for this one still.
Discussion: which joints, which wavelengths, and did pulsing vs constant make a difference for anyone here?
Short answer: near-infrared light is quite popular in sports areas for a reason — studies suggest it may support muscle recovery and reduce soreness, and it’s widely used by athletes, including some very famous football players :-)
Effects are however modest and protocol-dependent, so not miraculous.
Discussion: before or after training — what’s worked for you, and at what dose?
(personally I use for 10 mins on 100% for post-training)
Our short answer: The evidence for skin improvements is actually among the strongest in the field of red light therapy which probably explains the craze for masks. Reviews and clinical studies do report improvements in collagen, fine lines and skin texture with red/near-infrared light, and US dermatology reviews call it “promising and safe” for multiple skin conditions.
I will add some more links when I get a chance as there are quite a few out there.
Discussion: What wavelengths and time do people here actually use, and over how many weeks before seeing anything? Also do we think masks or panels better?
A community for people who want to know what red light therapy probably can and almost certainly can’t actually do — based on evidence, not just marketing, hype and sales bulls**t.
Obviously just because data is published we appreciate it is NOT guaranteed to be as beneficial as the studies show, but at least we can look at the source and decide for ourselves!
✅ Post studies, ask questions, and share proven data.
✅ Claims about benefits need a source — ideally peer-reviewed (PubMed/DOI).
✅ Label anecdotes as anecdotes. They’re generally welcome, they’re just not proof.
❌ No brand shilling, affiliate links, or hype.
❌ No cure claims or medical advice — see a professional for health conditions.
New here? Start with the pinned “Master Evidence List” and “How to read a red light study”.
This subreddit is founded and supported by Dermfix, an EU manufacturer of red light and UVB phototherapy devices. We started it because this space is full of marketing and short on evidence — and we wanted somewhere the actual studies get discussed. The rules apply to us too: claims need citations, and honest criticism stays up — including criticism of red light therapy generally, and of Dermfix. Mods will not remove a post just because it’s unflattering to a brand, ours included. You won’t see us dropping store links here; if you ever do, report it. If a study looks weak, say so. If the evidence for something is thin, we’d rather say “thin” than oversell it. That’s the whole point of the place.
