ALBAWABA Lightening dark armpits can be done effectively with simple, natural ingredients available at home. Here are some of the best methods to help brighten underarms: 1. Lemon and Baking Soda Scrub Ingredients : 1 tablespoon baking soda, ½ lemon Method : Mix baking soda with a bit of water to form a paste. Rub a lemon slice directly onto your armpit, then apply the baking soda paste in circular ...