Facebook apps can access various kinds of information once they are accessed or used.

Here is how to completely block a Facebook application  :

Login to Facebook and click on the inverted triangle at the top right. Then choose “Settings”.

 Click on the “Blocking” section from left.

Scroll down to “Block apps” and  enter the name of app to block. It will be added to block list. These added apps can at anytime be unblocked from here too if needed.

All done.