Redness in the face when it is hot in summer may be caused by physiological factors or pathological factors, such as rosacea, lupus erythematosus, etc. It is recommended that the patient be treated with medication under the guidance of a doctor to clarify the specific cause of the disease. 1. Physiological factors: In summer, when it is hot, the body temperature rises, and the capillary expansion will cause facial redness, which is a normal physiological phenomenon, and the symptoms will be gradually relieved when it is in a comfortable and cool environment, usually without special treatment. 2. Pathologic factors: (1) Rosacea: The facial skin barrier function of patients with rosacea is impaired, which can lead to blood vessel dilation after heat or sun exposure, resulting in redness in the face when it gets hot in the summer. Patients can use topical skin care products to repair the skin barrier, as well as oral with antibiotics such as doxycycline hydrochloride and antimalarials such as hydroxychloroquine, as prescribed by the doctor, for anti-inflammatory, anti-immune and anti-ultraviolet damage treatment. (2) Lupus erythematosus: The cause of lupus erythematosus is not known, and may be related to infection, immunity and other factors. In the high temperature of summer, especially after sun exposure, facial redness will occur. Patients need to systematically apply glucocorticoid drugs such as prednisone or immunosuppressants such as thalidomide under the guidance of a doctor to improve or relieve symptoms. When the phenomenon of redness occurs in the summer when it is hot, if physiological factors are excluded, it is recommended that the patient go to a regular hospital for examination, and after a clear diagnosis, standardized treatment under the guidance of a professional doctor.