An allergy sandwich is a peanut butter and strawberry jam sandwich. Lots of people have allergies to nuts and strawberries. The cool people, however, do not. They know the best pb&j is a pb with strawberry j.
Lulu: Oh man, what is that you're devouring?
Ramone: It's my allergy sandwich.
Lulu: What is that? It sounds disgusting.
Ramone: You are mistaken. An allergy sandwich is the magical combination of peanut butter and strawberry.
Lulu: Oh, yeah, I'm allergic to strawberries.