“....it’s the patients responsibly to be careful...”
I’ll take it a step further. Assuming that the “worker” in question was a typical grocery store clerk, the parents put him into an awful position. He or she must be feeling terrible now, knowing that they played a role in this child’s death.
It was really very unfair for the parents to place such a responsibility onto this worker’s shoulders.
I worked in a grocery store. I refused to answer allergy questions and referred them to read the ingredients themselves. They would get pissed off if I refused to tell then if something was safe for little Susie to eat.