When a baby has purpura, they typically exhibit skin petechiae, which are small red spots, often distributed around the joints of the lower legs and on the buttocks, appearing symmetrically and in varying sizes, which can merge into larger areas. These symptoms may gradually fade away within a few days but can recur. Additionally, the baby may experience gastrointestinal discomfort. The causes of purpura can include infections, food allergies, drug allergies, allergic reactions to pollen or insect bites, but the specific allergens are often difficult to determine. This condition is more common in children and adolescents.