Discolored skin

Ok I don’t know if anybody else here has this problem but basically anywhere on my body where skin touches skin and it sweats in between, my skin gets really dry and discolored. Like all the dry dead skin builds up and won’t go away and turns into a dark patch. It’s the worst under my armpits and it’s really noticeable and really embarrassing. I feel like it looks super gross. Does anybody else have this issue/know what it is/have any solutions for getting rid of the dark patches under my arms. Any advice would be appreciated ❤️