Allergic purpura, also called allergic purpura, is a kind of allergic capillary and fine vessel vasculitis, which mainly manifests as purplish petechiae and petechiae on the skin and mucous membrane, with severe joint pain, abdominal pain, kidney damage, and platelets will not decrease in patients with allergic purpura. Platelet reduction can also cause purpura, however, in addition to the occurrence of purple spots on the skin, often accompanied by nose bleeding, gum bleeding, mucous membrane bleeding, internal bleeding, etc., bleeding time and clotting time are prolonged, you can go to the hospital to check the blood routine to see the number of platelets, you can identify which is the case. If it is allergic purpura, check the urine routine accordingly to exclude kidney damage.