I am trying to figure out why the use of face bleach on underarm. I guess it's for the removal of black spots on that part of the body, or the stoppage of hair growth on the armpit or playing the role of deodorant, which is prevention of body odor. But whichever reason you want to make use of face bleach on your underarm, you have to first and foremost seek the wisdom of medical experts, because it might not be suitable for your health status.
Mind you that there are certain conditions that are health related which could be triggered by the use of any chemical on underarm. You don't want to take the risk of having any complications caused by face bleach on underarm. There is high tendency that if you are not having the type of body that is resistant to irritable issues as well as kidney problems, you shouldn't attempt the use of face bleach on your underarm, but if your body is compatible with it, you can give it a try.