Hello, my daughter has a rash on both her butt cheeks, she only wears a diaper at night, she's 4 years old. It looks a little dry, bright red, warm to the touch. Tried antibiotic cream for 2 days but didn't help. Tried petroleum jelly overnight last night, didn't help. It started about 1 week ago and has gotten bigger and redder. Tonight I am leaving the diaper off and I plan to switch washing detergents as well. What could be causing this and how can I get rid of it?