Red Light Therapy Does Not Cause Skin Cancer
Red light therapy (low-level laser therapy/LLLT) does not cause skin cancer and is fundamentally different from ultraviolet radiation-based phototherapies that carry documented carcinogenic risks.
Key Distinction: Red Light vs. UV Radiation
The provided evidence exclusively addresses ultraviolet (UV) phototherapy (narrowband UVB, PUVA, and photodynamic therapy using blue/UV light), which are entirely different modalities from red light therapy 1. These UV-based treatments carry well-established skin cancer risks, but this evidence does not apply to red light therapy.
Direct Evidence on Red Light Safety
DNA Damage Studies
- Red light does not induce DNA damage in human dermal fibroblasts, even at high fluences up to 1280 J/cm² 2
- Red light does not generate cyclobutane pyrimidine dimers (CPD) or 6-4 photoproducts (6-4PP)—the characteristic DNA lesions associated with UV-induced skin cancer 2
- Unlike UV radiation, red light does not create DNA adducts associated with skin cancer and photoaging 3
Tumor Growth Studies
- A controlled animal study using a standard UV-induced skin cancer model found that red light (670 nm) at 5 J/cm² twice daily showed no measurable effect on existing tumor growth over 37 consecutive days 4
- This suggests red light therapy may be safe even when malignant lesions are present 4
Mechanism of Safety
- Red light operates in the visible spectrum (typically 630-670 nm) and does not possess the photon energy required to directly damage DNA like UV radiation (280-400 nm) 5, 2
- While red light generates reactive oxygen species (ROS) in fibroblasts, this does not translate to DNA damage or carcinogenic potential 2
- Red light actually stimulates beneficial cellular processes including collagen and elastin production without inducing the p53 mutations characteristic of UV-induced skin cancers 6
Clinical Context
The confusion likely arises because:
- UV phototherapy (narrowband UVB, PUVA) carries significant dose-dependent skin cancer risk, particularly squamous cell carcinoma, with patients receiving >200 PUVA treatments having 30 times the risk of developing nonmelanoma skin cancer 1
- Photodynamic therapy (PDT) using blue or UV light with photosensitizers has theoretical carcinogenic concerns, though actual risk appears low with only rare case reports over 25+ years of use 1
- Red light therapy is fundamentally different and does not share these carcinogenic mechanisms 2, 3
Common Pitfall to Avoid
Do not conflate red light therapy with UV-based phototherapies. The extensive literature on UV phototherapy carcinogenicity (which dominates dermatology guidelines) does not apply to red/near-infrared light therapy, which operates through entirely different biological mechanisms and wavelengths 2, 4.