Allergic purpura is a systemic vasculitis syndrome with small vasculitis as the main lesion. The main clinical manifestations are skin purpura, joint pain, abdominal pain, blood in stool, and symptoms of kidney damage such as hematuria and proteinuria. The onset of the disease is more frequent in school-age children, with the age of 3-14 years being the preferred age. It can occur throughout the year, with more frequent occurrence in winter and spring. There are many allergic factors, including infections, food, drugs, pollen, insect bites, and vaccinations. Most children have a history of upper respiratory tract infection 1-3 weeks prior to the onset of the disease. It may be accompanied by systemic symptoms such as hypothermia, malaise and loss of appetite. The clinical manifestations mainly include skin purpura, joint pain, abdominal pain, hematuria, proteinuria, etc. Various symptoms can be combined in different combinations and appear in different sequences. The skin purpura is the first symptom, and in a few cases, abdominal pain, arthritis or kidney symptoms appear first. (1) Skin purpura The repeated appearance of skin purpura during the course of the disease is the characteristic of this disease. It is mostly seen on the extremities and buttocks, partly involving the upper extremities and trunk, and rarely on the face. The typical rash is initially small urticaria or purplish papules, which are higher than the skin and do not fade when pressed. (2) Gastrointestinal symptoms are mainly periumbilical or lower abdominal cramps with vomiting. About half of the children have positive fecal occult blood test, and some of them have blood in the stool or even vomit blood. (3) Joint symptoms: Multiple large joint swellings and pains, mostly in the knee and ankle, followed by the elbow and wrist, often with recurrent episodes, and fluid in the joint cavity is mostly plasma. Most of the joint symptoms disappear within a few days and no deformation is left behind. (4) Renal symptoms Renal symptoms vary in severity. Most children present with hematuria and proteinuria, and a few severe cases with swelling and hypertension are purpuric nephritis. (5) Other Central nervous system lesions are one of the potential risks of the disease, and intracranial hemorrhage, convulsions, coma and aphasia may occasionally occur.