My daughter started asking when she was 3. We didn't let her have it done then. She couldn't take care of them. I was a little scared she would get one caught on something, etc. When she was 5, she was constantly wearing screw-on earrings. They ended up causing some skin irritations she wore them so much......very cheap. After her ears scabbed over from that, we decided that she could have them pierced. This was age 5. I would have said that that was too young, too, but we only did it because she was going to keep some kind of skin reaction going to her play earrings, it seemed.
She was very happy at 5 to have them done, and she has been ever since. She's grown now. I would probably have said 10-13 would be old enough, though.