When a patient with lupus erythematosus sees a doctor, the doctor often asks: Has there been any rash or redness on the face or body? Has the rash worsened after sun exposure? Then why do doctors pay special attention to the sun exposure of SLE patients? Because when SLE patients are exposed to the sun, the ultraviolet radiation from the sun will not only aggravate the rash on the face or other parts of the body, but even aggravate the symptoms of the whole body, which is medically known as the phenomenon of “photoallergy”. Photoallergy is an important feature of lupus erythematosus and an important reason for the onset or aggravation of lupus erythematosus. We met a patient whose lupus symptoms were basically completely controlled by the doctor’s treatment and she could lead a normal life, so the doctor said she could get married. However, after the marriage they had one article that did not listen to the doctor and they went to Hainan Island for a trip. Because her husband didn’t know much about her inability to get strong sunlight and had already bought the tickets, and she herself was newly married and didn’t tell her husband about the situation because she was ashamed, so they went to Hainan and took a seawater bath. As a result, a rash appeared on her face again, her lupus flared up, and she had to be hospitalized again when she returned. Why are lupus patients particularly allergic to sunlight? Professor Sun Erwei’s group, with the support of the National Natural Science Foundation of China, conducted a study on this issue and put forward its own theory: UV rays in the sun have a damaging effect on the cells inside our skin, which can make the cells inside the skin damaged. In normal people, these damaged cells are quickly removed by a type of cell (called macrophage) in our body that is responsible for cleaning, and then new cells are quickly grown, so normal people can have peeling skin after strong sunlight exposure, but no rash, erythema or other symptoms of lupus. However, the macrophages of lupus patients are impaired and their ability to clean the skin is weakened, so when the patient is exposed to sunlight, the damaged cells in the skin cells cannot be removed in time, so these cells become “necrotic”, and the “necrotic” cells release a lot of “necrosis”. The “necrotic” cells release a lot of “bad molecules” that can inflame the blood vessels of the skin, thus aggravating the rash or causing a new rash to appear. At the same time, the necrotic cells also increase the activity of the immune system in our body, which then generates a series of reactions and finally produces something “bad” to destroy our own cells, making the systemic symptoms of lupus patients worse. The results of Prof. Sunil’s research were published in the international journals “Pharmacology and Therapeutics”, “Medical Hypotheses” and “Frontiers in Bioscience”. Frontiers in Bioscience”. The results were highly appreciated by the peers. Therefore, for patients with lupus erythematosus, sun exposure should be strictly prohibited, and they should be well protected in general, such as wearing wide-brimmed hats, long-sleeved shirts and sunglasses, etc. They must be well prepared for travel, and they should take measures to protect themselves from ultraviolet rays even on cloudy days, so that they can live a healthy and happy life.