As far as I understand, pet allergies are not like peanut allergies in that they're not actually lethal (correct me if I'm wrong!) As such, I feel like it's just one of those things that people might just need to deal with when they're part of a shared space much like sitting next to someone with bad body oder, someone chewing loudly, or someone laughing out loud when they're watching their tv. If it's too much of an annoyance maybe one can try to get moved to a different seat?