As soon as your face is red in the sun, you can observe it first. If it is just redness and soon returns to normal, it may be a normal physiological reaction. Because some people have white skin and less melanin, they may experience physiological redness under sun exposure, or prolonged exposure to sunlight may cause facial capillary dilation, resulting in redness of the face. Physiological reactions can recover on their own after they are removed from sun exposure and do not require treatment. In addition, a red face when exposed to the sun may also be due to pathological causes, including sunburn or UV allergy:1. Sunburn: prolonged exposure of the skin to the sun or too much light can lead to skin sunburn. Patients will have erythema on the face, and in severe cases, skin breakouts and blisters will occur. Treatment is based on local topical medication, with the principle of anti-inflammatory, soothing and pain relief, and generally topical stove glycolic lotion or glucocorticoids can be used. Usually to protect the skin, try to avoid prolonged exposure to the sun, prone to skin sunburn people also avoid eating photosensitive food, such as celery, fennel, mountain vegetables, etc.; 2, ultraviolet allergy: there is ultraviolet light in the sun, the people allergic to ultraviolet light a sun will appear the symptoms of blushing, and the degree of personal sensitivity to ultraviolet light. This category of people usually do a good job in life to protect themselves from the sun, use sunscreen gear when they go out, apply mild sunscreen products, and use anti-allergy drugs if necessary. If your skin is itchy and swollen after sunburn, don’t scratch it, pay attention to good skin cleaning, try not to wash your face with hot water and alkaline cleanser, and don’t apply heat to your face.