ok so my daughter has a really bad butt rash and I'm sure it was because her stool wasn't very good…

ok so my daughter has a really bad butt rash and I'm sure it was because her stool wasn't very good for a day she was a bit constipated... I tried desitin extra strength and it usually works and this time it hasn't I took her a bath with warm water and wipe her with warm cloth in a diaper change and other remedies you guys can recommend?