The treatment instrument is a kind of ultraviolet treatment instrument with wavelength between 311~312nm, it is divided into whole body and local instruments, the whole body machine is suitable for use in hospital, each treatment time is very short and very convenient. NB-UVB can treat a variety of diseases, such as psoriasis, vitiligo, pityriasis rosea, itchy rash, eczema, etc. In order to achieve better results and reduce side effects, please note the following precautions: 1. Avoid consuming photosensitive drugs and food during the photoperiod, and shield your eyes during photoperiod. 2. 2.No ointment and skin care products are used before the skin is illuminated, so that the skin can fully contact with the light and reduce the blockage of penetration. 3, light frequency generally 2~3 times a week, when the lesions are serious, the frequency can be increased to improve the efficacy, and so the lesions gradually improve, can slowly reduce the frequency, at least 7~10 days irradiation once, general irradiation 10 times for a course of treatment, generally need about 3 courses of treatment. Mild can stop irradiation after improvement, heavy 30 times not improved, can rest in January, and then repeat irradiation. 4, after each light skin may appear red, itchy, painful skin reactions, can be adjusted by adjusting the dose, frequency and topical emollients to reduce adverse reactions, light during the skin to avoid other light exposure, summer can wear long sleeves and long pants to cover. 5, the side effects of phototherapy are small and effective, and it has been widely quoted in the clinic, but it also has its contraindications and adverse reactions, short-term adverse reactions include erythema, itching, dry skin, pigmentation, etc., which can be avoided and improved; theoretically, long-term adverse reactions include photoaging, cataract, skin cancer and malignant melanoma, etc., but according to domestic and foreign research, there is no definite evidence that NB-UVB exposure leads to However, according to domestic and international studies, there is no definite evidence that NB-UVB exposure leads to an increase in human skin cancer. Therefore, NB-UVB is safe and effective.