In the comprehensive treatment of acne, for acne patients who are intolerant to medication or unwilling to accept medication, physical therapy can still be chosen. In recent years, we have mainly used simple narrow-spectrum blue light (415±5nm) and combined blue light and red light (660±6nm) to treat various types of acne vulgaris with good efficacy, featuring fast onset of action, short course of treatment and small adverse reactions, and inhibiting sebaceous gland secretion, reducing the number of acne and inflammatory lesions and promoting tissue repair to varying degrees. Principle of action: Propionibacterium acnes produces endogenous porphyrins during the metabolic process and accumulates in the bacteria. Narrow-spectrum blue light activates the endogenous bacterial porphyrins, resulting in a phototoxic reaction and the release of singlet oxygen, which efficiently kills Propionibacterium acnes without damaging normal tissues. Red light penetrates into the deeper layers of the skin, induces the release of cytokines from macrophages, affects the permeability of cell membranes to calcium ions, and has an anti-inflammatory effect. Indications: Suitable for patients with inflammatory lesions such as acne, pustules, red papular acne, etc. Red light can make acne “pimple marks” fade significantly. Treatment method: 2 times a week, blue light energy is 48J/cm2, red light is 126J/cm2, treatment 4-8 times for a course of treatment. Adverse reactions: slight itching in the treatment process, some patients showed slight flaking after treatment, no significant side effects were found. Precautions: Thoroughly clean the skin in the treatment area with warm water before irradiation, and avoid sun exposure for 3 days after treatment.