My 4 year old son has a half dollar size red rash on his left bum cheek. It is very red/purple in the middle and slightly lighter red around the perimeter? It does not have any blistering heAds and he says it does not hurt. I have not seen him scratching it until I touched it, then he said it doesn t hurt, but it itches, but not a constant itch. His father and I only noticed it yesterday, and I still help wipe after he has bowel movements, so I know it has not been there longer than two MAYBE three days. I did compare it to pictures of ringworm, and to me, it does not resemble that type of rash. Any suggestions ?