What causes dark spots under your armpit?

i think it is diskusting

ANSWER First, if you are going to say that something is digusting, please, for the love of God, spell it right...-_- Either way, having a pimple under your arm (in your armpit) is from sweating...Usually this happens during strenous activity... If you continue having this prouble, you should try and wear baby-powder, or another form of powder that will be able to absorb your sweat. In easiest terms, when you sweat overly much during strenous activity, such as running, the sweat has no place to go besides on the hairs under your arm and on your skin. Thusly, the sweat clogs your pores and you will end up with the sweat pimple. Hope this was helpful :-) ANSWER it's probably an ingrown hair which you get from shaving