Potty training rash?!

We've been potty training the past 2 weeks and my little boys come out on a rash on his bum cheeks and very top of his legs. I can not put my finger on what it would be as he's doesn't linger on the potty so it's not that he's wet. He hasn't shown any signs of it hurting until I put some E45 cream on it earlier. Also can't find any help on Google as its not like nappy rash