YES it is OK to use a bicarb soda deodorant, but only if it has been carefully formulated to have a lower pH like Woohoo.  We've carefully balanced the pH so it's not too alkaline but it still busts odour with the best of them.  It is possible your skin may react if you are using too much, have not properly cleaned away previous applications or have other external irritants like clothing rubbing on the area.  It’s also good to remember your pits occasionally need some moisturising just like the rest of your skin :-)  If you are extremely sensitive, which does happen for some, we do have Bicarb free Woohoo too!