Can Red Light Therapy Cause Cancer? What the Research Says

Red light therapy isn't known to cause cancer. The red (roughly 630 to 670nm) and near infrared (roughly 810 to 850nm) LEDs in home panels give out non-ionising light that doesn't carry enough energy to break DNA, which is how ultraviolet from the sun and sunbeds causes skin cancer. Reviews of the clinical research haven't found red or near infrared light starting cancer in healthy tissue. The one genuine open question is narrower, and it matters only if you already have cancer: whether light could nudge existing tumour cells to grow. That's the bit worth reading properly, along with who should speak to a GP before buying a panel.

Why red light isn't the same as UV

Most of the worry comes from lumping all "light therapy" together. Ultraviolet is the part of the spectrum sitting between X-rays and visible light, and the US Food and Drug Administration says prolonged UV exposure leads to skin cancer and premature ageing (FDA on ultraviolet radiation). Cancer Research UK is blunt about the mechanism: UV from the sun and from sunbeds damages the DNA inside skin cells, and that damage can build up quietly over years into skin cancer, melanoma included (Cancer Research UK on how sunbeds cause skin cancer).

Red and near infrared sit on the opposite side of visible light. Their wavelengths are longer, so each photon carries less energy than a UV photon does; not enough to knock electrons off atoms or snap DNA strands directly. The UV band stops at 400nm. A 660nm red LED is a long way past that, and an 850nm near infrared LED further still.

So the cancer risk you associate with sunbeds doesn't transfer to a red light panel, provided the panel really is red and near infrared only. That last condition is where cheap kit can let you down (more on that below).

What studies say about healthy skin

The best evidence here comes from the aesthetics world, where people sit under red and near infrared light for wrinkles and skin tone. A 2023 systematic review in Aesthetic Surgery Journal looked specifically at whether that light is oncologically safe (Glass, 2023). It pooled clinical trial safety data with lab work on human skin cells and cancer cells, plus animal tumour studies.

Its findings were fairly clean on the main question. Red and near infrared light tended to make healthy skin cells multiply without producing dysplasia, the abnormal cell changes that can come before cancer. In the clinical trials, nothing linked the light to serious adverse events, and that includes new or recurring cancers. The author concluded it's safe for aesthetic use, including in people with a cancer history.

That's encouraging, though the review itself admits most of the clinical studies were small and methodologically limited. "No evidence of harm" from small trials isn't the same as decades of population data, which nobody has for home panels yet.

The open question: existing tumours

This is the part most articles skip. Red and near infrared light work, as far as anyone can tell, by stimulating cell activity, mainly through the mitochondria. That's the whole point for recovery and skin. The worry is obvious: if light makes cells more active, could it make cancer cells more active too?

A 2020 systematic review in Cancer Medicine went through 67 studies on exactly this, covering cell lab work, animal experiments and human trials (Bensadoun et al., 2020). The picture splits by study type:

• Lab studies on cancer cells conflicted. Some cell lines grew faster under light, others slowed or died off, and the authors put much of that down to different doses and settings.
• Animal studies mostly showed no tumour promotion. A few did, though: a melanoma model in mice grew faster at very high doses (a lower dose had no effect), and a thyroid cancer model in immune-compromised mice showed more growth.
• Human studies, mainly head and neck cancer patients treated with light for mouth sores during chemo or radiotherapy, didn't show worse recurrence or survival. One small randomised trial even reported better outcomes, which the authors flag needs repeating.

Read that carefully. None of it suggests red light creates cancer. What it does show is that light can sometimes stimulate cells that are already cancerous, under certain doses, in certain models. The researchers called for more work on precisely that, which is why clinicians using light in cancer care follow set protocols and are cautious about aiming it straight at a tumour.

For a healthy person treating sore quads, this barely registers. For someone with active cancer, it's a real reason not to freelance with a home panel.

Who should check with a GP first

None of this is medical advice, and if any of the following apply, speak to your GP or oncologist before you buy:

• You have active cancer, or you've had skin cancer or melanoma. Don't treat over a current or former tumour site without your specialist's go-ahead.
• You take photosensitising medication, such as some antibiotics, retinoids or certain diuretics. Your pharmacist can tell you whether yours is one.
• You have an eye condition, have had eye surgery, or have light-triggered epilepsy and the panel has a pulse mode.
• You have a mole that's new, changing, bleeding or itchy. Get it looked at; don't light it.
• You're pregnant, simply because nobody has studied it well enough to say.

Eye safety deserves its own line, because it's the most practical risk with a strong panel. Near infrared is invisible, so a panel can look dim while still pumping out a lot of energy, and your blink reflex never kicks in. Wear the goggles. We go through this properly in our guide on how to use red light therapy.

How to buy a panel sensibly

If you're cleared to go ahead, the cancer question mostly comes down to buying a panel that is what it says it is. Four things to look for:

1. Stated wavelengths with no UV. The listing or manual should give exact figures, usually 630, 660, 810, 830 or 850nm. Vague claims like "full spectrum" or "multi-light" deserve a question to the seller before you pay.
2. Published irradiance at a stated distance. This is the power that actually reaches your skin, in mW/cm2. Wattage tells you almost nothing. A panel that quotes 132 mW/cm2 at 6 inches is giving you usable data; one that quotes a number with the sensor pressed against the LEDs is flattering itself.
3. Goggles in the box. Any panel bright enough to be useful should ship with them.
4. A timer. On a decent panel, 5 to 10 minutes per body area is plenty, and an auto shut off stops you dozing off under it.

Of the panels we've reviewed, the Hooga ULTRA360 is the most transparent about irradiance, publishing figures at several distances, and the trade off is a small treatment area. If you want something bigger for full body sessions, the Helios 2 Series 600W covers more skin, though Helios doesn't publish an independent irradiance figure.

Check the Hooga ULTRA360 price on Amazon

On a tighter budget, the BestQool 105W and the RENPHO panel are both spot treatment panels at around £190 to £200, fine for a knee or shoulder but not for full body sessions.

Is it worth it for recovery?

That's a different question from safety, and the honest answer is "maybe, modestly". The evidence for muscle soreness and recovery is mixed, with some decent trials and a lot of small, industry flavoured ones. We've pulled it apart in red light therapy for recovery, including the results that didn't work. If you're comparing it with heat, our red light sauna guide explains how the two differ.

Recommended reads

• How to use red light therapy: distance, time and dose
• Red light therapy for recovery: what the evidence supports
• Hooga ULTRA360 review
• Red light sauna: what it is and whether it's worth it
• All recovery gear and guides