TELL the other kids, parents, and teachers, etc. what it means. TEACH them how to prevent any problems.

It isn't getting through is it? Some children with nut allergy are at a life threatening risk if they come into contact with a person who has eaten nuts. Are you advocating segregation in schools? Seperate classrooms for nut allergists? Seperate sports changing rooms? Seperate dining halls? Seperate toilet facilities?

It is physically impossible to police who a child does and doesn't talk to or walk near at school. And neither should it be entertained as a solution.