The difference between photosensitized dermatitis and SLE lies in the definition, etiology, symptoms, and treatment. 1. Definition: photosensitive dermatitis is a skin lesion caused by sunlight exposure under the influence of photosensitizing substances, including solar urticaria, polymorphic sun rash, chemical photosensitive dermatitis and other diseases. Systemic lupus erythematosus is an autoimmune disease that can involve multiple systems. 2. Etiology: photosensitive dermatitis is caused by the patient’s sensitivity to ultraviolet rays as well as taking or contacting exogenous photosensitizers. The cause of SLE is not yet clear, but it is related to genetic, hormonal, immunologic and environmental factors. 3. Symptoms: Photosensitive dermatitis includes many types, such as solar urticaria, which is characterized by the appearance of a rash within 30 minutes after exposure to sunlight; polymorphic solar rash, which is characterized by an itchy rash that occurs 2 hours to 5 days after exposure to sunlight; and SLE, which has various symptoms, such as fever, fatigue, pterontic erythema and arthralgia. 4. Treatment: photosensitive dermatitis can be used externally with glycerite lotion to relieve itching, oral antihistamines such as loratadine, etc., to reduce the tissue inflammatory reaction. Systemic lupus erythematosus can be controlled by glucocorticoids, such as prednisone, etc., and immunosuppressants, such as mertiomacrophenol ester, etc., to control the progression of the disease and to prevent and control further damage to the organs. Photosensitive dermatitis is very different from SLE, so patients are advised to go to the rheumatology and dermatology departments of regular hospitals for detailed consultation.