The possibility of having purpura nephritis is considered to be high when the allergic purpura is cured but the urine keeps having occult blood, and the patient should seek medical examination in time. When allergic purpura skin symptoms healed, the patient urine occult blood has been positive, especially in the course of the disease within 6 months, consider the possibility of purpura nephritis. Patients need to go to the regular hospital in time to see the doctor for renal function, urine protein quantification, etc., and if necessary, renal biopsy pathology examination to clarify the pathological classification of the kidneys, and under the guidance of the doctor to determine the clinical typing of the disease and pathology typing. According to the typing of purpura nephritis, hormone therapy alone, hormone combined with tretinoin therapy, or hormone combined with other immunosuppressant therapy (e.g. cyclophosphamide, cyclosporine, tacrolimus, etc.) can be prescribed by the doctor. It should be noted that, after the disappearance of the skin symptoms of allergic purpura, the urine occult blood has been positive, even after the disease course of 6 months, should be promptly performed renal puncture biopsy to clarify the diagnosis. In addition, urinary occult blood is always positive after the disappearance of skin symptoms of allergic purpura, it is necessary to exclude whether the patient checks the urine routine after strenuous exercise, and it is also necessary to exclude whether the patient has renal injury before the occurrence of allergic purpura and other conditions. It is recommended that patients with positive urinary occult blood after the disappearance of skin symptoms of purpura should go to regular hospitals in time, and under the guidance of doctors for further examination and standardized treatment after a clear diagnosis.