What Causes Excessive Sweating In Under Arms?

hello my name is ebony and I was wondering why do I sweat under my arms so fast,especially soon as I get out the shower and I started 2 get dress and I always get real hot all the times so I will have 2 get the fan and turn it on because I always get a little 2 hot and I shave all the times and feel wet under my armpits real quick and I don't like the summer at all it's very embarassing