Photodynamic therapy is a new treatment technology that has emerged in recent years. It uses specific wavelengths of laser light to irradiate lesions that have absorbed photosensitizers, causing photochemical reactions that produce free radicals, singlet oxygen and other toxic substances, inducing apoptosis and necrosis of cells, thus achieving the purpose of treatment. Indications: (a) Acne: moderate to severe acne, especially cystic acne, nodular acne and various refractory acne. (b) Various viral warts: especially recurrent condyloma acuminata, flat warts, common warts, etc. (c) Skin tumors: basal cell carcinoma, Bowen’s disease, squamous cell carcinoma, paget’s disease (eczema-like carcinoma), etc. (d) Precancerous lesions: solar keratosis, value-added erythema, mucosal leukoplakia, Bowen-like papulosis, etc. (e) Infected skin ulcers: treatment of refractory ulcers, drug-resistant bacterial infection of skin ulcers, etc. The treatment advantages: 1, low recurrence rate can remove latent lesions, subclinical infection, thereby reducing the recurrence rate. 2, very little trauma With the help of optical fiber photodynamic therapy, avoiding the trauma and pain caused by surgery 3, low toxicity 5-ALA is the normal metabolic component of the body cells, normal tissue uptake less, fast metabolism. 4.Good selectivity The main target of attack is the lesion cells in the light area, and the damage to the normal tissue around the lesion is slight. 5.Protection of appearance and important organ functions For moderate to severe acne, flat warts and skin cancer on the face, it can effectively kill cancerous tissues while minimizing damage to the epithelial structure and collagen scaffolding of the diseased organ, preserving the integrity of organ shape and normal physiological functions. 6.No need to avoid light Compared with traditional photodynamic technology, 5-ALA has no photosensitivity, fast metabolism, and no need to avoid light, avoiding the advantages of retention of photosensitizer in the body and long avoidance time.