Purpura nephritis (anaphylatic purpura nephritis) is a kidney damage caused by allergic purpura, which can be caused by allergic reactions caused by bacterial, viral and parasitic infections, or by allergies to certain drugs and foods, or by plant pollen, insect bites and cold stimuli. In addition to skin purpura, joint pain, abdominal pain and blood in stool, the clinical manifestations are mainly hematuria and proteinuria, mostly occurring within one month after skin purpura, some may see skin purpura and abdominal pain at the same time, while some only have asymptomatic urinary abnormalities. If the protein loss is too much, nephrotic syndrome may appear. If hematuria and proteinuria persist for a long time, it may be accompanied by renal decompensation and finally lead to chronic renal failure. The proportion of allergic purpura leading to renal involvement is 20% to 100%, with more male patients than female.