The only person you can rely on is yourself, if for no other reason than mistakes happen (case in point).

And then what? Maybe your relatives can sue the company after you died. Fat lot of good that does for you.

Please don't blindly trust the labeling and exercise some basic common sense. Do you really want to be in the afterlife, thinking "well, the box didn't say milk, so how could I have known that butter contains milk"?