What Causes Circle Shaped Shadows On Legs, Arms And Abdomen?

My niece has had circle shaped shadows similar to a bruise since she was 6 mths old, she is now 5. They are approx 1-2cm in diameter and appear on legs and arms and abdomen- She has no pain or discomfort, and they come and go within 2-3 days of appearing, initially as a red cicle. They also seem to come in blocks, sometimes none at all and then suddenly a rash of them will appear. She has seen a GP and they mentioned something beggining with an E, I don t know what this is, but they also said this E thing usually affects adults and can be painful.Can you help?