It will be better to test this baking soda deodorant on the inner arm, before you apply it on the armpits. If there is irritation, you may mix more of cornstarch into it and try again. If you think that you are prone to skin irritation, then mix a part of baking soda with six parts of cornflour and use this mixture as a deodorant. If irritation still persists, it will be better to discontinue its use and opt for other homemade ones.