Dark underarms can be embarrassing especially during summer when you want to wear sleeveless. And minus points to have a black patches or dark armpit. Once you have realized the cause of these dark patches, you can also use the topical ingredients to lessen the patches. The easiest way to remove dark patches from underarm, sliced 1 tomato and rub it on the area of the patch. Leave it overnight and do it twice a day depending on how dark the patch is. During the day leave it on for 1 hour.