Red light therapy does not cause cancer. Unlike UV radiation — which damages DNA and raises skin cancer risk — red light operates at longer wavelengths that do not alter your DNA or trigger cancerous mutations. Current scientific evidence gives red light therapy a clear safety profile when it comes to cancer causation, and a growing body of research actually suggests it may have anti-tumour properties in certain contexts.

That said, the question deserves a thorough answer, because there are specific groups of people who should approach red light therapy with caution. Below we break down exactly what the science says, how red light differs from harmful UV, and who should speak to a doctor before starting sessions.

Key Takeaways

Red light therapy uses wavelengths of 630–850 nm — far too long to damage DNA or cause cancer.
UV radiation, not red light, is the type of light linked to skin cancer development.
Multiple systematic reviews have found no evidence that red light therapy causes or promotes tumour growth in healthy individuals.
Some early research suggests red light may actually inhibit certain cancer cells, including melanoma — though this is not a treatment and more research is needed.
People with existing cancer or photosensitive conditions should get medical clearance before using red light therapy.
The FDA classifies red light therapy devices as Class II medical devices with an established safety profile.
Red light therapy is commonly used in oncology settings to reduce treatment side effects such as oral mucositis and radiodermatitis.

What Is Red Light Therapy and How Does It Work?

Red light therapy (also called photobiomodulation or low-level light therapy) uses specific wavelengths of visible red and near-infrared light — typically between 630 nm and 850 nm — to penetrate the skin and stimulate cellular function. Unlike UV rays, this light does not carry enough energy to cause direct damage to DNA.

At the cellular level, red light is absorbed by mitochondria, the energy-producing structures inside your cells. This absorption boosts ATP (adenosine triphosphate) production, reduces oxidative stress, and triggers a cascade of repair and regeneration signals. The practical results include improvements in collagen production, wound healing, inflammation, and skin tone.

It is worth being clear about what red light therapy is not: it is not UV therapy, it is not laser ablation, and it is not photodynamic therapy. Each of these is a distinct treatment with its own risk and benefit profile. Conflating them is one of the most common sources of confusion around this topic.

Why Red Light Therapy Does Not Cause Cancer

The Key Difference: Wavelength and Energy

The reason UV radiation causes skin cancer is specific: UV rays (UVA at 315–400 nm and UVB at 280–315 nm) carry enough photon energy to cause direct DNA damage, creating mutations in skin cells that can lead to malignancies over time.

Red light sits at 630–700 nm, and near-infrared at 700–850 nm. At these wavelengths, the photon energy is significantly lower. The light cannot break chemical bonds in DNA, cannot cause the kind of pyrimidine dimers that UV creates, and has not been shown — in any credible study — to initiate cancerous mutations. This is not a gap in the research; it is a well-understood photochemistry principle.

The skin benefits of red light therapy stem precisely from this lower-energy interaction: it stimulates without damaging.

What Systematic Reviews Actually Say

The most rigorous way to assess a safety question like this is to look at systematic reviews — studies that pool data across many individual trials. The picture here is reassuring for healthy individuals.

A major 2020 systematic review published in Cancer Medicine by Bensadoun et al. analysed 67 studies on photobiomodulation therapy in cancer patients — including in vitro, in vivo, and clinical data — and concluded that clinical studies did not demonstrate tumour promotion or accelerated recurrence. [Bensadoun et al., Cancer Medicine, 2020]

A 2023 systematic review in the Aesthetic Surgery Journal by Graeme Glass specifically examined the oncologic safety of low-level light therapy used for aesthetic skin rejuvenation — essentially the kind of device use most consumers will encounter. After reviewing 25 years of literature, the review found no compelling evidence that photobiomodulation causes malignant transformation in normal skin. [Glass, Aesthetic Surgery Journal, 2023]

A more recent 2024 review in Frontiers in Oncology by Luitel et al. further evaluated photobiomodulation’s role in oncological treatment and found it was being increasingly integrated as a supportive care tool, with no identified signal for cancer induction. [Luitel et al., Frontiers in Oncology, 2024]

Can Red Light Therapy Actually Fight Cancer Cells?

This is where the research gets genuinely interesting — though it is important to be precise about what the evidence does and does not show.

A 2022 study published in Frontiers in Oncology by Austin et al. irradiated melanoma cells with red LED light in both in vitro and animal models. The results showed that red light decreased cellular proliferation and, at higher fluence, increased apoptosis (programmed cell death) in melanoma cells. In animal models, it significantly reduced tumour growth. Importantly, red light caused no skin inflammation or damage to normal surrounding tissue. [Austin et al., Frontiers in Oncology, 2022]

This is a striking result — but it is preclinical data. It does not mean red light therapy is a treatment for melanoma. What it does suggest is that red light at therapeutic parameters does not appear to encourage melanoma growth; if anything, the opposite may be true. Human clinical trials are needed before any therapeutic claims can be made.

Red light therapy is also used in oncology settings today — not to treat cancer directly, but to manage treatment side effects. Multiple trials and the World Association for Laser Therapy position paper have documented its value in reducing side effects like oral mucositis, radiodermatitis, and fatigue in people undergoing chemotherapy and radiation.

Who Should Exercise Caution With Red Light Therapy?

For the vast majority of people, red light therapy carries no meaningful cancer risk. However, a few groups should get medical advice before using it:

People with Active Cancer

The concern here is not that red light causes cancer — the evidence does not support that. The concern is theoretical: red light promotes cellular activity and blood flow, and there is not yet enough data from large clinical trials to definitively rule out any effect on certain tumour types. For this reason, oncologists often advise caution and case-by-case assessment for patients with active malignancies, particularly those that are photosensitive.

Those with Photosensitive Skin Conditions

Conditions such as lupus erythematosus, porphyria, or certain drug-induced photosensitivities can cause reactions to light exposure even outside the UV spectrum. If you have a condition that makes your skin abnormally reactive to any light, consult your dermatologist first.

People Taking Photosensitising Medications

Some medications — including certain antibiotics, anti-inflammatories, and psychiatric drugs — increase light sensitivity. This does not make red light carcinogenic, but it can cause skin reactions. Check with your doctor or pharmacist if you are on regular medications.

Pregnant Women

Not due to cancer risk, but because red light therapy has not been adequately studied in pregnancy. The precautionary principle applies here.

Red Light vs UV: A Clear Distinction

It is worth spelling this out plainly because some people — understandably — link any kind of light therapy to the known risks of UV exposure from tanning beds or the sun.

UV radiation is the culprit behind photocarcinogenesis. It works by penetrating skin cells and directly damaging DNA, particularly through the formation of pyrimidine dimers. Over time, with accumulated exposure, this can lead to basal cell carcinoma, squamous cell carcinoma, or melanoma. This is why tanning bed risks are taken seriously and why SPF use matters.

Red light therapy contains zero UV. It operates in an entirely different part of the electromagnetic spectrum. Grouping the two together would be like worrying that the red light in a darkroom causes the same damage as standing in full midday sun — they are simply not the same thing.

How to Use Red Light Therapy Safely

Assuming you are in good health and have no contraindications, red light therapy is considered low-risk when used correctly. A few sensible practices:

Protect your eyes. While red light does not emit UV, looking directly into high-intensity panels can cause eye strain or discomfort. Use the protective goggles that come with most devices.
Follow recommended session times. More is not necessarily better. Most devices recommend 10–20 minute sessions. Overexposure won’t cause cancer, but it can cause skin irritation and diminishing returns on photobiomodulation effects.
Choose a reputable device. FDA-cleared devices (Class II) have undergone safety evaluation. Cheap, unvalidated panels may not deliver consistent wavelengths or safe power outputs.
If you have any skin lesions or unusual spots, get them checked first. Not because red light will worsen them, but because any new therapy is best started from a baseline of knowing your skin is healthy.
If you are undergoing cancer treatment, speak to your oncologist. As discussed, PBMT is used in oncology as a supportive tool — but always under medical supervision.

For more on getting the most from your sessions, see our guide to how red light therapy works and what to realistically expect.

Frequently Asked Questions

Does red light therapy increase the risk of skin cancer?

No. Red light therapy uses wavelengths that do not damage DNA, which is the mechanism through which UV causes skin cancer. Multiple systematic reviews have found no evidence that red light therapy raises skin cancer risk in healthy individuals.

Can red light therapy make existing cancer worse?

This remains an area of ongoing research. In vitro data on several cancer cell lines shows mixed results depending on wavelength, dose, and cancer type. The clinical evidence available does not show tumour promotion, but people with active cancer should always consult their oncologist before starting red light therapy.

What does red light do to cancer cells?

Early preclinical research suggests red light may inhibit the proliferation of certain cancer cells, including melanoma, and trigger apoptosis. However, this does not mean it is a treatment for cancer. Much more clinical research is needed before any therapeutic conclusions can be drawn.

Is red light therapy FDA approved?

The FDA classifies red light therapy devices as Class II medical devices. Several have received 510(k) clearance for specific applications including skin rejuvenation and hair loss treatment. The FDA’s position is focused on claims — not on flagging red light as a cancer risk.

Who should avoid red light therapy altogether?

Those with active cancer (without medical clearance), photosensitive skin conditions such as lupus, those on photosensitising medications, and pregnant women should either avoid it or consult a doctor first. Eye protection should always be used during sessions.

Is red light therapy the same as laser cancer therapy?

No. Medical laser cancer treatments (such as photodynamic therapy) are distinct procedures that use light-activated chemical agents to destroy cancer cells. Red light therapy at home or in wellness settings is low-level, non-ablative, and operates at much lower energy outputs.

Can I use red light therapy if I’ve had skin cancer in the past?

Discuss this with your dermatologist. There is no clear evidence that red light therapy promotes recurrence, and some practitioners use it on patients with a history of skin cancer. Your individual situation, location of the previous cancer, and current skin health will all factor into that guidance.

The Bottom Line

Red light therapy does not cause cancer. The photochemistry is clear: red and near-infrared wavelengths do not have the energy to damage DNA, and the clinical literature — including multiple systematic reviews — supports a reassuring safety profile for healthy users.

The more nuanced reality is that people with active cancer or certain photosensitive conditions should get medical clearance before using it, and that red light is not a treatment for cancer despite some early, promising preclinical findings. Used correctly, with a quality device, it remains one of the safer non-invasive wellness tools available.

If you are new to red light therapy and want to understand the broader picture of what it can and cannot do for your skin, our complete guide to red light therapy benefits is a good next step.

References

Bensadoun RJ et al. Safety and efficacy of photobiomodulation therapy in oncology: A systematic review. Cancer Medicine, 2020.
A PRISMA-compliant systematic review of 67 studies on PBMT in cancer patients. Clinical studies did not demonstrate tumour promotion or increased recurrence rates, supporting the oncologic safety of photobiomodulation.
Austin E et al. Red Light Phototherapy Using Light-Emitting Diodes Inhibits Melanoma Proliferation and Alters Tumor Microenvironments. Frontiers in Oncology, 2022.
Preclinical in vitro and animal study showing that red LED light inhibited melanoma cell proliferation and increased apoptosis at higher doses, without causing inflammation in normal tissue.
Glass GE. Photobiomodulation: A Systematic Review of the Oncologic Safety of Low-Level Light Therapy for Aesthetic Skin Rejuvenation. Aesthetic Surgery Journal, 2023.
A 25-year literature review examining whether PBMT used for cosmetic skin treatment poses any malignant risk. Found no compelling evidence for carcinogenic effects in normal skin.
Luitel B et al. Reviewing the efficiency of photobiomodulation therapy in oncological treatment. Frontiers in Oncology, 2024.
Comprehensive 2024 review evaluating the supportive use of PBMT in oncological care, finding growing evidence for its role in managing treatment side effects without promoting tumour growth.