The redness of the skin when exposed to the sun is mostly related to physiological and pathological factors (including solar dermatitis, rosacea, etc.), which need to be clarified after the specific disease, and then take the appropriate treatment to deal with it. 1. Physiological factors: Usually, after the skin is exposed to the sun, due to the expansion of the skin capillaries, it will lead to temporary redness of the skin. After leaving the sunlight, it will recover by itself and will not affect the health of the body, so there is no need for treatment. 2. Pathological factors (1) solar dermatitis: if the sun is too strong, exposure time is too long, easy to cause epidermal cell necrosis, release a variety of active mediators, causing dermal vascular edema, skin redness. Normally, avoid exposure to the sun, if necessary, follow the doctor’s instructions to use topical glucocorticoid therapy, such as hydrocortisone cream. In severe cases, the use of boric acid solution wet compresses and antihistamine treatment, etc.. (2) Rosacea: This disease may be an inflammatory skin disease of the face caused by various reasons. Mostly in the sun and other hot environment when the attack, can be manifested as facial redness, burning, itching, or pimples, pustules, etc.. Normally, attention should be paid to sun protection, when the attack can use medical cold compresses cold compresses, at the same time with the soothing yellow light treatment. In addition, should follow the doctor’s instructions external tacrolimus cream, oral ebastine antihistamine and other comprehensive treatment. It is recommended that patients who suspect that the disease is caused by a timely visit to the dermatology department of a regular hospital, by a professional doctor for standardized diagnosis and treatment.