Allergic purpura is a vasculitis syndrome with systemic small vessel inflammation as the main lesion, clinically manifested as platelet non-reducing purpura, often accompanied by joint swelling and pain, joint effusion, abdominal pain, blood in stool, and hematuria. The disease occurs throughout the year, with spring and autumn being the most common seasons. The pathogenesis is related to the genetic predisposition of the individual. This means that an as yet unidentified source of infection or allergen, acting on an individual with a genetic background (the affected child), causes an abnormal immune response in the body, stimulating the proliferation of B-cell clones and leading to IgA-mediated systemic immune vasculitis. Predisposing factors often include: microbial (bacterial, viral, parasitic, etc.) infections, drugs (antibiotics, salicylates, isoniazid, phenobarbital, etc.), food allergies (fish, shrimp, eggs, dairy), vaccinations, pollen allergy, mosquito bites, etc. However, there is no definite evidence for any of them.