Discoulored dry skin under arms

I've had this dry skin on my chest for about three years now. It doesn't really bother me but it's not going away. It's just under my arm pits and it has an orange/brownish colour. The skin is a bit flaky but it doesn't itch more than other skin.

I took some ACUTANE for my acne as a teenager and I think it might be related to that. I also have dry cracked skin on my neck quite often, but that isn't discoloured. I jog regularly and the dry skin is right were my arms rub against my chest. However the skin doesn't heal when I stop jogging during the winter.

I tried applying some moisturizing lotion for a couple weeks but that didn't help. I would like to know if there's anything else I should try, or if this could be more than just dry skin.

Thanks.