Best remedy for severe diaper rash?

My son daycare hasn't been changing my son diaper very good. He has a bad rash where its all red with blisters thats its starting to bleed just a bit. My son has also been screaming and crying on top of his lungs because he is in severe pain from the rash. I have been putting Vaseline, Destin on it. This daycare he goes to. A kid bit my son underneath his arm so the daycare had to do a police report. This daycare isn't no good taking good of kids. They don't watch them very closely like most daycare workers do. Any remedies on any particular rash cream that works like a charm?