"Oh uh..." Richie had never really had to explain it before, "it's like when your immune system thinks something you ate is bad for you but it's messed up and reacts too much and if it's real bad it makes your throat close up and you die." He'd done a lot of looking in to it once, when he thought Eddie was really allergic to all of the things his mother said he was. He'd even gotten Ediie to show him how to work his epi-pen once.
"I don't think it's usually that bad, but it can be." he shrugged.