Suggest Remedy To Get Rid Of Dark Lines In Armpits

Hello. I'm a female from Philippines. It's in our genes to have line folds on the armpits both my mom and dad. It was not visible before but when I reached adolescent, it started getting darker. My armpit is not dark, it's the lines that makes it darker. I'm 21 and it's still not disappearing no matter what I do. Any suggestions how to lighten/get rid of these lines? Thank you!