Armpit sweat is one of the main causes of body odor. Sweat and bacteria combine to create an unpleasant odor. There are daily actions you can take to keep your underarms healthy and clean. 1. Deodorize regularly The armpit is where body odor most often appears. Accumulated sweat and dirt cause odor, while poor hygiene can make underarms oily, clogged and itchy. A good way to avoid this is to use a deodorant product that effectively neutralizes odors. Starting with daily deodorant will help your armpits smell less bad.