Visible red light does not induce DNA damage in human dermal fibroblasts

Visible red light (RL) therapy is a rapidly expanding treatment option for dermatological conditions, including acne, psoriasis and chronic wounds. It is currently unknown if high fluences of RL induce DNA damage via reactive oxygen species (ROS) stress or other pathways. Our lab previously demonstrated that RL generates ROS in human dermal fibroblasts (HDFs). Other studies show that UV and blue light generate ROS and DNA damage in fibroblasts. This study aims to determine if RL induces DNA damage in HDFs. We found that 320 J/cm², 640 J/cm² and 1280 J/cm² RL (633 ± 6 nm) did not measurably increase DNA damage in the form of cyclobutane pyrimidine dimers (CPD) or 6-4 photoproducts (6-4PP) immediately, 3 hours and 24 hours following irradiation. Our study further supports that RL therapy is safe in human skin fibroblasts.