One of my coworkers has a daughter, 9 years old, who is allergic to peanuts. So I asked her what they do. She said they just toss the candy she can't eat. Or rather, they gave it to her nephew who happened to be visiting. We had a back and forth conversation about it and here's the gist of what she told me.
The daughter understands her peanut allergy and understands that she has to be careful about what she eats. She (the daughter) reads labels and avoids things that have been manufactured in places which have peanuts (although apparently she can eat some of those things). She doesn't get upset or disappointed about things she can't eat as she's pretty used to it. I was listing out the candy we had handed out last night, kitkat, whoppers, reese's & hershey's milk chocolate. Coworker said, oh, she can eat all of those except the reese's!
So, that's just one perspective but my coworker was really casual about the whole thing. I got the idea that, sure, it's an inconvenience and they hope she will outgrow the allergy as they test her periodically, and she has outgrown some other food allergies, but in the grand scheme of things, it's just not that big a deal. They deal with it and don't make it out to be anything to get in a twist about and the daughter takes it mostly in stride.