There are many reasons for itchy back, the common ones are urticaria, contact dermatitis, eczema, ringworm, pruritus and so on. 1. Hives: usually induced by contact with food, drugs, environment, physical factors, etc., is a kind of allergic reaction. It is mainly due to the increase of skin permeability and capillary dilation, resulting in the appearance of skin tingling, accompanied by itching. 2. Contact dermatitis: when the skin on the back comes into contact with external sensitizers, it may cause redness, swelling and itching of the skin at the contact site, which may also lead to itching on the back. 3. Eczema: Inflammatory skin reaction caused by internal and external factors, related to infection, endocrine, environmental, food and other factors, may appear on the back, causing itchy back. 4. Ringworm: Fungal infection caused by ringworm may also cause itchy back, and may cause skin flaking, erythema and other symptoms. 5. Pruritus: mainly refers to itchy skin without primary skin damage. It may also cause itchy back. Pruritus is divided into local pruritus and generalized pruritus. Visceral tumors and mental stimulation may cause generalized pruritus. There may be other causes of itchy back, and you need to go to the hospital in time to confirm the diagnosis.