Ultraviolet light can treat psoriasis, vitiligo, and other pigment loss diseases, and the side effects include the following: 1. Skin cancer: long-wave ultraviolet and medium-wave ultraviolet among the ultraviolet rays in sunlight are capable of inducing skin cancer. Among them, medium-wave UV is the main reason for destroying melanocyte genes and inducing the development of cancer. Long-wave UV can suppress certain functions of the immune system and can accelerate the formation of tumors. In daily life, it is necessary to do a good job of sun protection and avoid exposure to the sun in the hot sun, and at the same time apply sunscreen or isolation cream when going out, and do a good job of physical sun protection, such as playing umbrella, riding in a car, wearing a hat. 2, pigment-like deposition: when UV treatment for skin diseases, if the dose is too large, it will cause pigment-like deposition, pigment-like dermatitis or pigmentation formation, because the UV dose is too large, causing a large number of melanin 3, other side effects: for the original eczema patients, if long-term exposure to ultraviolet radiation, there may be photosensitive reactions, eczema increasingly aggravated, and the circumference of erythema, papules, rice-like blisters, and even increasing fluid exudation. The number of eczema is increasing. Therefore, for patients with eczema, it is important to pay attention to UV protection.