Bumps on the skin after scratching may be caused by hives, atopic dermatitis and other diseases. 1. Hives: Hives often begins with itching, followed by the appearance of bright red, skin-colored or white bumps. They can last from a few minutes to a few days and usually leave no trace when they subside. After scratching the itchy skin bumps, much like a special type of urticaria – skin scratching urticaria, is due to a reaction to external mechanical stimuli, that is, in the skin to produce wind. 2. Allergic dermatitis: If one is allergic, intake or contact with some allergens such as milk, fish and shrimp food, etc., may lead to itching and swelling of the skin, but also pimples, erythema, blisters, etc., and blisters can occur when the inflammation is intense. When patients with severe skin rashes, they need to go to the hospital in time, do not use medication without authorization, so as not to delay the condition.