How could something be so painful?

No, I'm not talking about childbirth. I'm wondering aloud how something on my baby's body could be so painful to me. Gabriel has some really wicked diaper rash. Since I'm always putting stuff on him when I change his diaper, and I change his diaper every time I feed him (about every 1.5 to 2 hours), I wonder how he got such a bad case of diaper rash. Mom tells me that it could be something I ate, since I'm breastfeeding. Anyway, my point was that I see how painful it is to him when I change him. It is not the tangible pain of being pinched. It is looking at his raw little butt and cringing from the pain that I imagine he is feeling. I'm normally very empathetic, but I suppose this is the empathy of motherhood. I can't stand to see my baby in pain, and I would do anything to bear that pain in his place. It has started looking a little better, but if it doesn't clear up in a couple days, I'm calling the doctor.