Red light exposure to the eye is risky and can result in damage to the retina.[1] For this reason, red light therapy for eye conditions should only be performed under the guidance of a qualified medical professional.
Eye use excluded, red light therapy appears to be fairly safe, with reported side effects tending to be rare and mild (e.g., itchy skin, acne, and skin tenderness).[2] Red light exposure can also produce a sunburn-like effect if the power intensity and duration of exposure are high enough. Interestingly, individuals with darker skin pigmentation appear more susceptible to this effect (unlike with ultraviolet light exposure, where the opposite is true).[3]