[Jacq-i]

Maybe a skin-lightening cream? There are a couple different ones at Sephora...

Otherwise, just moisturizing + exfoliating... Although that could be tricky. I tried putting a lotion on my underarms, after I accidently cut it with a razor. A couple of hours later, I has no idea why one of my underarms was sweating, but it was because that lotion was clogging my skin. Whoops!

Now your thread has me looking at my underarms. They're dark too. lol