Itchy skin after running is considered to be related to seasonal allergies and cholinergic urticaria. 1. Seasonal allergy: If you are allergic to substances in the air, such as pollen, dust, animal dander, you may have an allergic reaction. Contact with or inhalation of the above substances during running may cause an allergic reaction, leading to itchy skin. 2. Cholinergic urticaria: Itchy skin after running may be cholinergic urticaria, which is also a kind of urticaria. After exercise, the body’s heat production increases, resulting in the proximal part of the trunk and limbs appearing in different degrees of wind, erythema, accompanied by obvious itching sensation. Itchy skin after running, it is recommended not to scratch the stimulus, to avoid inducing infection, if necessary, to the hospital dermatology department, under the guidance of the doctor to give medication.