Nothing - provided the ink doesn't run. A bar-code is a physical system - not electronic. So long as the bars are still intact, the reader will still recognise the series of stripes.
only if it smudges or the lines vertically and damaged. Bar-code are very resilient as they are used in frozen and chilled product sales.
It gets disappeared when if it gets wet.
Then the ear gets wet...
it gets wet
He gets wet
it disolves
it gets wet
It gets rusty and smells funny.
None, unless it gets wet.
It changes color and
it gets wet.
It breaks