For dark underarms, you can use alum (tawas). It also removes or prevents body odor. There are several ways of using or applying it and all are effective.
If you want a dry underarm deodorant, you can apply powdered alum directly to it.
If you want it in liquid form, you can follow either of the following mixture:
-- Use 1 Whole alum pound to small pieces (w/ small chunks not powdered). Add 1 bottle of Ginebra San Miguel (Gin). Add several drops (or more if needed) of your favorite perfume or cologne.
-- Or 1 teaspoon powdered alum, 1 cup water and a few drops of your favorite perfume or cologne.
To use the liguid mixture, you can either use a spray/spritzer or cotton balls. You can actually use this for the whole body especially if you perspire a lot. It really prevents body odor and whitens your skin.
You can buy alum or tawas from the grocery, drug store or market.
I had been using this for the longest time since I have sensitive underarm skin. My underarm gets dark and a couple of times develeped bumps (due to blocked pores) when I use other deodorants.
Try this and see its great effect.