Allergic purpura is a common capillary allergic disease, the main pathological basis is extensive capillary vasculitis, with skin purpura, gastrointestinal mucosal bleeding, painful joint swelling and nephritis as the main clinical manifestations, a few patients also have angioneurotic edema. The degree and regression of renal involvement is an important factor in determining the prognosis. Allergic purpura can occur at any age, but it is more common in children and adolescents, especially in preschool and school-age children, and less common in infants under one year old, and more common in males than females (about 1.4 to 2.1:1). How many types of allergic purpura are there? 1, simple type (purpura type): the most common type, mainly manifested as skin purpura. Purpura often occurs repeatedly in batches, symmetrical distribution and other characteristics, can be accompanied by skin edema, urticaria. The purpura is dark red at first and does not fade when pressed, it may fuse into patches or slightly above the skin surface, showing a hemorrhagic rash or small urticaria, and in severe cases it may fuse into large blood sores with hemorrhagic necrosis in the center. The purpura gradually turns into purple, yellow-brown, yellowish within a few days and gradually fades away after 7 to 14 days. 2, abdominal type (Henoch type): In addition to skin purpura, there are a series of gastrointestinal symptoms and signs, such as nausea, vomiting, vomiting blood, diarrhea and mucus stool, blood in stool, etc.. Abdominal pain is the most common, often with paroxysmal colic. The abdominal signs mostly appear at the same time with the skin purpura, and may occasionally occur before the purpura. 3, joint type (Schonlein type): In addition to skin purpura, there are also joint swelling, pain, pressure pain and functional impairment. It occurs in large joints such as knee, ankle, elbow, wrist, etc. It is wandering, recurrent, and heals after several days without leaving joint deformity. 4, renal type: the incidence can be as high as 12% to 40%. On the basis of skin purpura, hematuria, proteinuria and tubular urine appear, occasionally edema, hypertension and renal failure are seen. The renal damage mostly occurs 1 week after the appearance of purpura, or it can be delayed, and most of them recover within 3-4 weeks; a few cases evolve into chronic nephritis or nephrotic syndrome due to repeated attacks. 5, mixed type: skin purpura combined with other clinical manifestations. 6, other: a few patients can also be involved in the eye, brain and meningeal vessels and related symptoms and signs.