What is Red Light Therapy?

Red light therapy (RLT) has been gaining a lot of attention in integrative health and wellness. In scientific and clinical research, it’s often referred to as photobiomodulation (PBM) or low-level light therapy (LLLT).

It involves exposing the body to red and near-infrared light (usually from a panel, lamp, or mask) with the aim of influencing cellular signalling involved in recovery and repair.

If you’ve come across it and you’ve been affected by cancer (or you’re supporting someone who has), it’s completely understandable to wonder:

Can red light therapy cause cancer?
Can it cause cancer cells to grow or stimulate tumour growth?
Is red light therapy safe for cancer patients?
Could it help with cancer treatment side effects (such as radiotherapy skin reactions, oral mucositis, or neuropathy)?
Are there risks, and when should it be avoided?

In this article, we’ll explore these questions in a clear and evidence-informed way, including how PBM interacts with mitochondria, how it differs from photodynamic therapy (PDT), what the research says about tumour safety, and what to consider if you’re thinking about using red light therapy at home.

Red light therapy & cancer: the key safety points

Red light therapy uses non-ionising red and near-infrared light (unlike UV light or X-rays), so it isn’t generally linked to DNA-damage-driven cancer risk.

However, when cancer is part of the picture, the more important question is whether red light therapy could influence existing tumours under certain conditions (dose, location, cancer type, timing).

A cautious, sensible approach is to:

Avoid using red light therapy directly over known or suspected tumour sites unless it is part of a clinician-led protocol and approved by your medical team.
Be particularly cautious around radiotherapy treatment fields, where skin can be fragile and protocols vary between centres.
Consider medication and individual factors that may increase light sensitivity.

Red light therapy is most often discussed in cancer care as supportive care (helping manage treatment side effects), not as a cancer treatment.

How Red Light Therapy Works

Red light therapy typically uses wavelengths in the red (roughly 620–700 nm) and near-infrared (roughly 700–1100 nm) ranges. These wavelengths can penetrate the skin to different depths, depending on the device and settings.

Researchers believe a key target of red light therapy is the mitochondria — often described as the “energy centres” of the cell. When mitochondria absorb certain wavelengths of light, this may influence:

cellular energy production (ATP)
signalling involved in repair and inflammation
molecules such as reactive oxygen species (ROS) and nitric oxide (NO)

Red light therapy effects can be dose-dependent (sometimes described as “biphasic”), meaning more isn’t always better. Outcomes may vary depending on the tissue, the person, the device, and how Red light therapy is used.

What’s the difference between photodynamic therapy (PDT) and red light therapy (RLT)?

Because both involve “light”, PDT and Red light therapy are sometimes confused — but they are not the same intervention.

Photodynamic therapy (PDT)

Photodynamic therapy is a medical treatment used for certain skin conditions and some cancers. It involves applying or giving a photosensitising drug that accumulates more in abnormal cells. A specific light is then used to activate the drug, producing a reaction that damages targeted cells. PDT is carried out under clinical supervision and has a clear therapeutic intent.

Red light therapy / photobiomodulation (PBM)

Red light therapy / (PBM) does not use a photosensitising drug. It uses red and near-infrared light with the goal of influencing cellular signalling involved in repair and inflammation.

In cancer care, Red light therapy is most often discussed in the context of supportive care (for example: radiotherapy skin reactions, pain, wound healing support, or oral mucositis) — not as a cancer treatment itself.

Mitochondria, cancer, and red light therapy: why it’s nuanced

When you bring cancer into the picture, Red light therapy becomes more complex.

The same signalling pathways involved in healing and repair are also involved in cell growth and immune activity. That means Red light therapy’s effects can vary depending on:

the tissue being treated
the person’s physiology and treatment context
the cancer type and activity
and critically: dose, frequency, and location

This is why “Red light therapy is always safe” and “Red light therapy is always dangerous” are both oversimplifications. The most sensible approach is to interpret the evidence cautiously and apply conservative safety rules.

Can Red Light Therapy Cause Cancer?

Many people worry about this because Red light therapy can support repair and cellular signalling. Some clinicians have historically been cautious, especially because therapies that influence healing pathways could theoretically influence tumour-related pathways under some conditions.

What we know in simple terms

Red light therapy uses non-ionising light, so it is not the same type of exposure as UV or ionising radiation.
The more relevant question in cancer is not “does it cause cancer?” but:
could it influence existing tumours under certain conditions?

Can red light therapy cause cancer cells to grow?

This is the question many people are really asking — and it deserves a careful answer.

Evidence from an animal safety study (non-melanoma skin cancer model)

A paper by Myakishev-Rempel (2012) looked at a practical tumour-safety question in an established mouse model where mice develop multiple non-melanoma skin cancers after UV exposure.

Once visible tumours were present:

one group received 670 nm red LED light to the whole body twice daily (a total of 5 J/cm² per day)
for just over five weeks
the control group was handled the same way without the light

The researchers measured tumour growth over time using standardised photographs. In this set-up, red light did not measurably increase tumour growth compared with controls over the study period.

How to interpret this:
This is reassuring for that specific model and protocol, but it doesn’t prove safety for all cancer types, all doses, or in humans. It supports a cautious conclusion: Red light therapy may not automatically need to be ruled out purely because cancer is present — but context, dose, and location matter, and more research is needed.

What about melanoma or skin cancer?

If you’ve had melanoma (or you’re worried about it), it’s natural to wonder whether Red light therapy could be risky — especially because Red light therapy can influence cellular signalling and repair.

A study by Austin (2022) explored melanoma models in the lab and in mice. This is important: it was not a study in people. The exposure times used were far beyond typical home use:

melanoma cells in the lab were exposed for 2–4 hours
mice received red light daily for 4, 6, or 8 hours depending on the dose

That matters because Red light therapy can be dose-dependent, and extremely long exposure times don’t translate cleanly to typical home protocols.

What the researchers reported (in this model):

in the lab, red light was associated with slower melanoma cell growth at lower tested doses
at higher doses, there were signals consistent with increased programmed cell death
in mice, the highest dose was associated with slower tumour growth in this model
the authors also noted changes in markers in skin surrounding the tumour that they discussed as potentially relevant to immune activity

How to interpret this:
This doesn’t prove Red light therapy treats melanoma in humans, and it doesn’t mean home devices are “anti-melanoma”. It’s an early research signal in a highly controlled context using unusually long exposure durations.

Practical safety rule:
If you have current melanoma/skin cancer (or you’re under investigation), don’t use Red light therapy over the lesion area unless your dermatologist/oncology team explicitly approves it.

Is Red Light Therapy Safe for Cancer Patients?

One review (Paglioni, 2019) pooled 27 human clinical studies where photobiomodulation (PBM) was used for cancer treatment toxicity it concluded from the current literature that:

Photobiomodulation (red light therapy) did not find evidence of tumour-safety concerns in the clinical studies reviewed when PBM was used to manage treatment toxicities.

While research on red light therapy’s role in cancer is still limited, and more prospective studies with long-term follow-up are needed; there are certainly some studies suggesting it may provide benefits for cancer patients in specific ways:

Supporting skin reactions from radiotherapy
Helping with Oral Mucositis, dry mouth, mouth ulcers
May help reduce symptoms of Chemotherapy-Induced Peripheral Neuropathy
Support Breast cancer-related lymphoedema

Where Red light therapy may help during cancer treatment (supportive care)

Can Red Light Therapy Help with Dermatitis from Radiotherapy?

Radiation dermatitis (sore, red, peeling or ulcerated skin) can occur during radiotherapy, particularly in head and neck cancers.

A clinical study (Zhang, 2018) looked at whether red light phototherapy could help:

60 patients were split into two groups
both received routine skin care
one group also received Red light therapy for 10 minutes, twice daily, throughout radiotherapy

In this study, dermatitis grades were generally milder and pain scores were lower during weeks 2–4 in the Red light therapy group.

Clinical reality:
Radiotherapy teams vary in what they allow on the treatment field. If you’re having radiotherapy, don’t use a home device on the radiotherapy field unless your radiotherapy team has explicitly advised it.

Can Red light therapy help with oral mucositis during cancer treatment?

Oral mucositis is painful inflammation and ulceration in the mouth, which can occur during chemotherapy and radiotherapy (especially in head and neck cancer).

Red light therapy has gained interest in oncology supportive care partly because oral mucositis is often highlighted as one of the more established supportive-care applications in this context (for example, discussed in Hamblin, 2018).

Key point:
This is discussed as a way to support comfort and treatment tolerance — not as a cancer treatment.

In practice, this is typically done using specific protocols and devices under professional guidance, rather than improvising with a high-powered home panel.

Chemotherapy-induced peripheral neuropathy (CIPN): why people are looking at Red light therapy

CIPN can cause tingling, numbness, burning pain and altered sensation, often in the hands and feet, and it can persist long after treatment ends.

An overview (Lodewijckx, 2020) notes CIPN is common, with rates reported around 68% in the first month after chemotherapy (falling over time, but still affecting many people months later).

The same overview highlights why there is interest in new options:

many approaches are limited to symptom management
severe CIPN can sometimes contribute to chemotherapy dose reduction — which is a major clinical trade-off

Red light therapy is discussed as a potential supportive therapy, but the authors stress that:

evidence is still limited
studies use very different protocols and outcomes
which makes it hard to draw firm conclusions.

Can Red light therapy help prevent or reduce CIPN during chemotherapy?

A small randomised, placebo-controlled pilot trial (often referred to as NEUROLASER) explored whether Red light therapy could help prevent CIPN in breast cancer patients receiving taxane-based chemotherapy.

32 patients were randomised to Red light therapy or placebo treatment twice weekly during chemotherapy
symptoms were tracked with validated neuropathy scoring, plus quality-of-life and function measures

The main neuropathy score worsened over time in both groups, but several patient-reported sensory neuropathy symptoms worsened in the placebo group while remaining more stable in the Red light therapy group. The Red light therapy group also showed better quality-of-life scores during chemotherapy, and there were signals favouring Red light therapy at follow-up for walking capacity and pain.

Bottom line:
This is promising early evidence, but it’s not strong enough yet to treat Red light therapy as a proven prevention strategy. Larger trials are needed before this could be considered a reliable standard approach.

Both CIPN discussions also acknowledge why tumour safety has been debated: Red light therapy can influence repair signalling, and parameters vary widely. The broader supportive-care literature is generally reassuring, but ongoing monitoring and better standardisation are important.

Breast cancer: where Red light therapy has been studied for supportive care

A review (Robijns, 2017) looked at low-level light therapy as supportive care in breast cancer — meaning support for side effects rather than treating cancer itself.

They reported the most consistent promising findings in areas such as breast cancer-related lymphoedema, with additional early evidence across radiotherapy skin reactions and other symptom-management applications in specific contexts.

The review also makes an important point: it can be difficult to compare studies because protocols vary widely (device type, wavelength, dose, and frequency). The therapy may be encouraging for certain side effects, but stronger evidence and clearer protocols are still needed before it could be considered “standard”.

Using red light therapy during chemotherapy or radiotherapy

Many people asking “can red light therapy cause cancer?” are actually asking a practical question:
“I’m on treatment now — can I use a home device safely?”

During chemotherapy

If you’re in active chemotherapy, consider:

Photosensitising medications: ask your oncology team whether any of your medications increase light sensitivity
Skin sensitivity: avoid Red light therapy on areas that are inflamed, broken, blistered, or slow-healing
Hygiene: keep devices clean, especially if you’re immunosuppressed
Avoid ports/lines areas: don’t treat directly over central lines or ports
Start low and slow: shorter sessions, lower intensity, and increase only if well tolerated

During radiotherapy

Radiotherapy skin can be fragile and reactive, and departments vary in guidance:

Don’t treat the radiotherapy field unless your radiotherapy team approves it
Avoid anything that increases irritation or heat
Ask about timing, skincare rules, and whether Red light therapy is appropriate in your specific situation

How to Use Red Light Therapy at Home

Using red light therapy at home is straightforward but involves following a few essential steps to ensure safe and effective use.

Look for device specs: wavelength bands, irradiance at a stated distance, and recommended dose (J/cm²)
Target the Right Areas: Decide where you want to focus treatment based on your health goals.
Avoid use overknown or suspected malignancy sites unless part of a clinician-led protocol & been cleared to do so by your medical team.
Prepare the Skin: Clean and dry the treatment area to ensure the light penetrates effectively.
Position the Device: Follow the manufacturer’s guidelines for distance and treatment time, typically around 15-20 minutes per session.
Protect Your Eyes: Avoid looking directly at the light. Some devices come with eye protection, but you can also use goggles or keep your eyes closed.
Stay Consistent: For best results, regular sessions over several weeks are recommended.
Observe Progress: Consider tracking your progress with photos or notes to see how the therapy works for you.

Remember, while red light therapy is generally safe, it’s always wise to consult your healthcare provider, especially if you have any pre-existing conditions or are taking medication.

Red Light Therapy Product Recommendation:

Red Light Rising sell various sizes of red light therapy devices. To get 10% off use code MCN10 - shop red light therapy here.

(Disclosure: if you purchase via this code/link, I may receive a small commission at no extra cost to you.)

Frequently Asked Questions

Red and near-infrared light are non-ionising, so Red light therapy isn’t generally linked to DNA-damage-driven cancer risk. The more relevant concern is whether Red light therapy could influence existing tumours under certain conditions (dose, location, cancer type, timing). A cautious approach is to avoid Red light therapy over known or suspected tumour sites unless clinician-led.
Some clinicians have raised this as a theoretical concern because Red light therapy can influence repair signalling. An animal study in an established non-melanoma skin tumour model did not show increased tumour growth at the tested settings, which is reassuring for that set-up — but it doesn’t prove safety in all cancers or all circumstances.
Evidence in humans is strongest for Red light therapy as supportive care for treatment toxicities, with literature reviews generally describing tumour-safety findings as reassuring in those contexts. However, suitability depends on diagnosis, treatment type, location, and dose — and it’s sensible to be cautious during active treatment.
It may be appropriate in some contexts, but extra caution is sensible due to skin sensitivity, medication-related photosensitivity, and infection risk. Keep devices clean, avoid broken or inflamed skin, avoid ports/lines areas, and start with conservative dosing.
Don’t use a home device on radiotherapy fields unless your radiotherapy team has explicitly approved it. Radiotherapy skin can be fragile and reactive, and guidance varies across centres.
Red light therapy has been studied as supportive care for issues such as breast cancer-related lymphoedema and some symptom-management contexts. However, protocols vary widely and individual factors matter — especially if radiotherapy has been involved in the area you want to treat.
Preclinical studies don’t automatically translate to home use. If you have current melanoma/skin cancer or a suspicious lesion, don’t use Red light therapy over that area unless your dermatologist/oncology team approves it.
A randomised clinical study in people receiving radiotherapy for head and neck cancer found that adding red light phototherapy (10 minutes, twice daily, alongside routine skin care) was linked with milder skin reactions and less skin pain, particularly during weeks 2–4 of treatment, compared with routine care alone.
An overview paper describes PBM as a promising supportive option for CIPN, while emphasising that studies use different protocols and outcome measures, which makes firm conclusions harder.
A randomised, placebo-controlled pilot trial (NEUROLASER) in breast cancer patients receiving taxane chemotherapy found that neuropathy worsened over time in both groups, but several patient-reported sensory neuropathy symptoms worsened more clearly in the placebo group, with signals favouring PBM for quality-of-life and some functional outcomes. Larger trials are still needed.
Oral mucositis is one of the most established PBM applications in oncology supportive care. An umbrella review of randomised trials notes PBM has been included in clinical guidance for oral mucositis, reflecting a comparatively mature evidence base in this area.

Conclusion

Red light therapy (photobiomodulation) uses non-ionising red and near-infrared light and is being studied primarily as supportive care in oncology — for example, to help with side effects such as oral mucositis, radiotherapy skin reactions, and potentially neuropathy symptoms in some contexts.

At the same time, tumour-safety questions are valid. The most sensible approach is to treat Red light therapy like any other intervention during cancer care: use conservative dosing, avoid applying it directly over known or suspected tumour sites, and get clinical guidance if you’re on active treatment — especially radiotherapy, where skin can be fragile and protocols vary between centres.

Interested in working with an Oncology Nutritionist for cancer prevention or following a cancer diagnosis? Get in touch to chat about how My Cancer Nutritionist can help you.

Book Complimentary 30 Minute Call

Red Light Therapy & Cancer: Benefits, Risks, Safety, and How to Use It at Home

What is Red Light Therapy?

Can red light therapy cause cancer?

Can it cause cancer cells to grow or stimulate tumour growth?

Is red light therapy safe for cancer patients?

Could it help with cancer treatment side effects (such as radiotherapy skin reactions, oral mucositis, or neuropathy)?

Are there risks, and when should it be avoided?