One of the more unique remedies for dark underarms comes in the form of sandalwood, namely a paste made from this ancient herb. You can apply this nutrient-concentrated paste directly to the underarms, where the many acids, volatile components and nutrients of sandalwood cleanse the skin cells and reduce inflammation. While the sensation may be a bit strong for some with sensitive skin, this is a fast and effective way to lighten those darkened areas of your skin. Sandalwood is readily available at many health food stores and herbal remedy shops.