How To Get Rid Of Painful Chaffing In My Upper Thigh?

It's summer and i have been getting very frequent and painful chaffing in my upper thighs. This happened last summer also and the chaffing will then turn into a boyle or an infected bump or something. I have tried clyndemisen (ziana) on it which i use for acne and diaper rash cream and cleaning it but it wont go away! how do i get rid of chaffing/prevent the boyles from forming?