The causes of small red blood spots on the body include allergic purpura, cherry angioma, spider nevus and other diseases. 1. Anaphylactic purpura: It is an inflammation of blood vessels, the onset of which is related to infection, food, drugs and other factors. When purpura allergic occurs, it increases the fragility of capillaries, causing blood to break through the capillary endothelium more easily, which results in the formation of bruises or blood spots under the skin. At the same time, this disease can lead to painful symptoms in joint muscles, as well as abdominal pain and proteinuria. 2. Cherry angioma: the cause of the disease is still unclear, and it can also be called senile hemangioma. The disease is caused by the expansion and proliferation of skin capillaries. It will lead to the appearance of small red blood spots on the body. 3. Spider nevus: related to sex hormone metabolism change, can be seen in pregnant women, patients with liver disease or normal people, is a kind of idiopathic capillary dilatation, for the skin of small arterial branches at the end of the expansion of the formation. It can lead to the appearance of small red blood spots on the body. When there are small red blood spots on the body, it is recommended to go to the hospital dermatology department as soon as possible to clarify the specific causes of the disease, so as to facilitate the treatment of the cause, so as not to delay the condition.