Itchy bags on the body for no reason, may be acute urticaria, contact dermatitis, mosquito bites and other causes. 1. Acute urticaria: Often itchy skin occurs after being cooled or blown by the wind, and soon the itchy place appears as a reddish wind mass. 2. Contact dermatitis: If the skin on the body is in contact with allergenic substances such as ointment, it can cause the body to have an abnormal immune response, which may cause the bag to appear for no reason, accompanied by itching. 3. Mosquito bites: If you are bitten by mosquitoes without realizing it, the acids in the mosquito saliva can cause an allergic reaction in the body, resulting in itchy bumps. It is recommended that the body is very itchy for no reason to go to the hospital in a timely manner, clear reasons, such as the need for treatment, should be standardized treatment under the guidance of a doctor.