I don't know what to do

my 5 year old daughter has this thing where she always sticks her hand in her butt crack. I am unsure if she's actually scratching it or what. She says it's wet ,so she does it. I am guessing maybe she has crack sweat and tries to wipe it with her hands? I bathe her and doubled checked that she wasn't red or anything down there. My husband put a little powder on her crack to see if that helps her feel drier, but she flipped out and wiped it all off. I have never dealt with this, but its gross and I don't know what else to do. I hate to say this, but you can almost smell it on her when shes been digging or scratching. I have had talks with her and I make her wash her hands as soon as I notice, but she wont wash on her own. What do I do? She starts kindergarten soon, I dont want her doing this there.