Sweating under my neck and lips cause brown spots to appear how do i stop and remove them?

It may not be: Due to sweat. If i had to say, it may be pigmentation increases that may be due to elevated insulin. Not sure but if you have a family hx of type 2 diabetes, say, and could stand to lose weight, look up acanthosis nigricans to see if that fits ur description. Good luck, it's improvable if that is the case, may consider endocrinologist but see pcp first.