Are they red? Is there any broken skin, or other evidence of irritation?
He could just have dry ears... I think there's a cream you can get for dry ears, though I'm not sure what it's called. Maybe someone else could chime in?
It could just be dry skin. How often does he get a dust bath? Depending on climate 1-2 times a week could be enough for the bath. If his skin is getting dried out he may be getting it too often. You can get bag balm to put on his ears.