How come the acid inside the human digestive system eats away at food but not at the guts around it?

Question

I was just wondering, how come it can devour food completely, but you cant even feel it?

Answer 1

It does eat away at your stomach at times.  If you are in the hospital for an extended amount of time and can't eat, they will put you on an acid reducer so your body will produce less because if not, the acid will "eat" away at your stomach lining.  If the acid has nothing to work against, it works against you.  Also this happens when people get ulcers, etc.  

Answer 2

Well the stomachs interior has a protective layer of "mucous membranes" that prevent the acid from hurting the stomach.