I am only moderately not a biologist, but this seems essentially correct -- vaccines are trying to address false negatives, but allergies are (in theory) caused

I am only moderately not a biologist, but this seems essentially correct -- vaccines are trying to address false negatives, but allergies are (in theory) caused by false positives. The mechanics of T cell training in the thymus for self/nonself discrimination are only partially understood, but any approach to rewrite antigen recognition would be (A) extremely risky, by potentially inducing massive autoimmune effects if anything went wrong, and (B) much more impactful for e.g. organ transplantation than allergic response.