I hv dark underarms too and went searching on d net for home treatment. Found a few method,some pretty ma fan so i tried d easiest,scrub & exfoliate. I had some expired st ives apricot scrub dt i found too rough 4 my face,so i started using it for underarms daily. This is a slow but cheap process,i only see improvement after few weeks,but it does help. I already did this for 2 months,it's definitely helping,but again,slow. It's cheap,i only finished about 3/4 bott after so long. Oh ya,i still shave.

This is also recommended if u use deoderent too coz even if it has whitening pigments,it still contain chemicals,best to wash it all off when u bathe. Sometimes washing with soap not enough(learnt fr somewhr,coz i dun use deodarent)