Purpura nephritis is not contagious. Purpura nephritis is an IgA vasculitis and is not an infectious disease. Allergic purpura mainly involves the skin, gastrointestinal tract, joints and kidneys. When allergic purpura involves the kidneys, we call it purpura nephritis. Patients often present with hematuria or proteinuria, and some patients may present with nephrotic syndrome, which is a manifestation of massive proteinuria, hypoproteinemia, edema and hyperlipidemia. In addition, purpura nephritis may also manifest as other systemic involvement, such as a rash that occurs mostly on the extremities, but can also occur on the buttocks or trunk as bleeding spots slightly above the skin, which may appear in batches and fuse together. When the gastrointestinal tract is involved, it may manifest as abdominal cramps, nausea, vomiting, black stools, and fresh blood. When accumulating to the joints, it may manifest as pain, joint effusion and pressure pain in the ankle or knee joints.