Nothing at all. Balloons will pass normally through the digestive tract with no problems.
You'll choke and die
put them in a balloon tie the balloon and swallow it.
If you swallow a balloon you will most likely suffocate and die. This may sound a little over the top however it is likely that the balloon will wrap itself round your lungs and will disrupt your respiratory system. On the other hand, a balloon might block one of your vital arteries or might get stuck in your throat. If you swallow a balloon you should call an ambulance immediately.
I suppose it depends on the size, but not a regular party size ballonn.
You Die
you die
pain
you die...
Nothing happens
The balloon expands.
The balloon will either float or pop
You can get chemical burns along your throat and stomach if you swallow lye.