The reasons for the redness of the face after running include physiological reasons, such as capillary expansion after normal exercise; also includes pathological reasons, such as cholinergic urticaria, solar dermatitis and so on. 1. Physiological reasons: the face is rich in capillaries, running and other sports to speed up blood circulation, capillary expansion leads to redness, not accompanied by other discomforts, after running and resting for a period of time, the face can return to normal, this is a normal physiological phenomenon, no need to be overly concerned about the gradual increase in the amount of exercise, pay attention to the post-exercise supplementation of water can be. 2. Pathologic causes: (1) cholinergic urticaria: when strenuous exercise, elevated body temperature, emotional stress and other factors may induce urticaria, in addition to the red face, it will also be manifested as a whole body erythema, wind masses, etc., this situation needs to consult a doctor in a timely manner to clarify the diagnosis, and the use of cetirizine, glycerol lotion and other medications under the direction of the doctor. (2) solar dermatitis: after exposure to ultraviolet radiation, the face will have erythema with itching, prolonged exposure to the sun may also appear blisters, vesicles, moulting, etc., daily outing without sunscreen will also appear similar symptoms, not limited to running, may be sunburned or ultraviolet light allergy, after diagnosis, daily outing need to pay attention to sunscreen. If after running and resting, the redness can subside in a period of time, it is not necessary to care; if accompanied by other discomforts such as erythema, it is recommended to consult a dermatologist in time to clarify the diagnosis, and standardize the use of medication under the guidance of the doctor.