Allergic purpura is one of the common diseases in children, which belongs to autoimmune disease, and the rapid onset is its prominent feature. In recent years, the incidence of allergic purpura is on the rise, the incidence of children aged 6 to 14 years old is higher, and most of the sick children are allergic. The causes of pediatric allergic purpura are as follows 1, infection: such as pediatric colds, tonsillitis, pneumonia, diarrhea, urinary tract infection, skin sores, etc. About half of the sick children have a history of upper respiratory tract infection 1-3 weeks before the onset of the disease. 2, food: such as fish, shrimp, eggs, milk, wine, drinks, soy products, leeks, beef jerky, etc., can cause the onset of allergic purpura, or make those who have been treated to improve relapse. 3, drugs: such as penicillin, sulfonamides, biological agents, various preventive injections, plasma products, blood, etc. 4, toxins: such as bee, snake, scorpion, mosquito bites, etc., may also cause the onset. 5, certain foreign substances: such as pollen, willow, pet’s fur, and paint, gasoline, dust, chemicals, pesticides, chemical fibers and so on, the affected children can develop the disease because of contact. 6, in the recovery period of allergic purpura, strenuous exercise may be one of the important factors for recurrence. 7, drinking cold yogurt and other dairy products: the proteins in yogurt as allergens stimulate the intestinal tract is very easy to cause microvascular bleeding and allergic symptoms. What are the manifestations of pediatric allergic purpura? Allergic purpura is a hemorrhagic disease caused by damage to small blood vessels throughout the body, and the body undergoes a metamorphic reaction. School-age children are the susceptible group of this disease, and they often have a history of upper respiratory tract infection before the onset of the disease, and the onset is rapid. It may manifest as bleeding spots on both lower limbs, symmetrical, varying in size, mostly beginning to appear on the bilateral lower legs, around the ankle joints, sometimes accompanied by urticaria, and in more severely ill children bleeding spots may also appear on the upper limbs, chest and back, and even large petechiae or bloody blisters. Purpura is characterized by bleeding spots that are high on the skin, varying in size, purplish in color, and do not fade when pressed. It usually subsides in 1 to 2 weeks, but many children may have recurrent or prolonged disease for weeks, months or even longer. Some children may also have abdominal pain, joint pain, and even kidney damage such as proteinuria and hematuria. Some children have painful swollen joints and are unable to walk. It is mostly seen in the ankle and knee joints, and some children even develop joint cavity effusion. The characteristic of joint swelling is that it does not leave after-effects after it subsides. A few children have pain around the umbilicus, vomiting, and even blood in the stool and intussusception. In some children, renal damage, such as hematuria, proteinuria or tubular urine, may occur, and this more severe manifestation is called purpura nephritis, which usually occurs 2 to 4 weeks after the onset of the disease. The onset of nephritis varies in severity, most are mild and usually do not heal on their own, a few can develop renal failure and uremia. Allergic purpura can easily involve the kidneys of children, most of them can recover after systematic treatment, but if not treated systematically and repeatedly, a few can develop into chronic nephritis and even renal failure. So the affected children should have regular urine tests and should do a good job of kidney protection while undergoing allergic purpura treatment.