I think this can somewhat depend on the degree of reaction. My sister has kids with peanut, dairy, and egg allergies. For the peanut, because nut allergy reactions can be SO severe, she keeps it out of her house (and the rest of us did as well when her kids were little). For dairy and egg, although the reactions are anaphylactic, at least for her kids, they're *less* serious (we're all well aware the next time it might be more serious), so for those, she's just really careful, but her other family members consume dairy and egg, in the house.
Pick battles big enough to matter, small enough to win. ~Jonathan Kozel