There is no data to support the effect time of photodynamic therapy for nevus erythematosus and it is impossible to judge. Due to the patient’s condition and physique are different, its effect time is also different. Photodynamic therapy is to inject chemical photosensitizer intravenously, which can increase the sensitivity of the lesion area to light, and after appropriate amount of irradiation, it can cause light-heat and photochemical reaction within the capillaries, thus destroying the blood vessel wall, so as to achieve the therapeutic effect. For patients with good physical condition and mild disease, after treatment with photodynamic therapy, the effect time is relatively fast. For patients with poor physical condition and more serious condition, the effect time may be relatively slower. It is suggested that patients with nevus erythematosus should go to regular hospitals for consultation and treatment under doctor’s guidance after the cause of the disease is clarified, so as to avoid delaying the condition.