What Causes Bumps On The Hands?

Many small bumps showed up on my 12 yr old daughters hands a couple of days ago mostly on the top of her finger joints, do you think applying cortosone cream on them will help, or should I be using something else. They are small round about the size of this text ( O ) maybe a little bigger but not much. They are the same color of her skin not red or inflamed. What do you think is causing these bumps to appear