Allergic purpura mainly occurs in adolescents and children, often in the spring and autumn seasons, and is typically related to bacterial infections, viral infections, and allergies to medications and foods. The most common clinical symptoms include bruises on both lower limbs, bleeding, black stools, joint pain, and abdominal pain. Upon the appearance of bruises on the lower limbs, it is recommended to complete routine blood tests, erythrocyte sedimentation rate, and autoantibody tests to rule out other autoimmune diseases causing skin bruises. During the acute phase, it is necessary to rest in bed, drink plenty of water, and eat a light diet. If there are only simple skin bruises, these may resolve after rest. However, if joint pain, bloody stools, and black stools occur, formal and active treatment is required, as these symptoms will not resolve on their own. Additionally, the presence of blood or protein in urine suggests kidney involvement, indicating that the condition has worsened.