Quoting Baby Love.:" Maybe the diaper just irritated him. Or his skin was moist and just rubbed together?"
Quoting Erica Hunt:" My daughter does the same thing with certain diapers. Maybe try another brand"
Quoting ♫Kaibutsu♫:" But at the top of his hip? That spot doesn't get wet which is why I'm confused."
Quoting Baby Love.:" Maybe the diaper was just to snug or rubbed him the wrong way."
Quoting Squeaky McGee:" Does he wear jeans with elastic in them? Sometimes my daughter's jeans rub her hip area and leave little red spots."