Why does hydrogen peroxide bubble?

Question

why does it bubble when it touches a cut, sometimes your toe nails and inside the ears sometimes?

Answer 1

because the bubbles are the bacteria coming out of wat ever you put it on

Answer 2

2 H2O2 --> 2 H2O + O2 - and the O2 is a gas coalescing inside a liquid, so it bubbles.  Or appears to.  Not quite the same reason that soda and beer form bubbles, but the same effect.

Answer 3

Yes, as doc. stated, the bubbles are oxygen gas being released as hydrogen peroxide breaks down into water and oxygen gas.  This happens when it comes in contact with cuts, because it is an oxidizing agent, this also causes it to be a good antiseptic (and bleach at higher concentrations).  

Wikipedia has more details and information if you are interested.