Here's a test:
I'll keep a webcam recording myself during work for the next hour, now.
I will try to remind myself not to touch my face and will keep a tally sheet of how many times I successfully restrained myself, and often I caught myself touching it.
Then I'll review the video material and see how many times I've not even witnessed touching my own face during that hour.
[Just typing this post, I've already touched my own face 7 times]