Does anyone know what this might be?

My DS's ear yesterday afternoon went really red, it almost looked purple at one point and looked a little puffy and it felt warm. It then over the next few hours went back to normal and was fine this morning, then this afternoon it went red again (not as bad as yesterday) and was warm to the touch.
DS reckons it doesn't hurt and he is fine in himself, eating normally, sleeping well, heaps of energy.
Is it likely to be an ear infection?

TIA