blimey, oh rilley, what a kerfuffle. I think it is totally reasonable for nutella to be banned in the school if a child is extremely allergic. As posters have no doubt said, it is often enough just to come in contact with an allergen.
I think the raise in allergies reflects what is in our food rather than an altered reaction to them. For years and years we have used pesticides and god knows what on our foods. This could have easily, indirectely modified the genes of certain plants in order to cope with the chemical onslaught. Genomes don't change over night, but over time - it might be that we are now seeing the results of splashing the fields with DDT and suchlike - just a theory - i haven't done any research into allergies.
They are certainly more commonplace, the older generation always seem to be a bit when i say, i want DD to avoid nuts and seafood until she is about five (isnt that the recommended age?) because i have hayfever and have once had an anaphylactic reaction to something we never identified (thankfully it was a one off). Its always the same, well XYZ have eaten nuts etc and they are fine. Thats it, most people are fine, some people aren't. But something has changed recently and i don't think its us humans.
I do think that there is a misconception and im sure people will agree or disagree with me on this, that often a person is described as allergic when it is a case of intolerance, which physiologically is a completely different thing, but in some cases just as debilitating.
Maybe all schools should ban nutella, it tastes like shit anyway and im sure it would be better used as an adhesive