That's the way life goes Osc, sometimes vibes are needed months in a row, sometimes all at once, but then hopefully none at all for ages
It's very frightening, especially when you are first dealing with it, remember little Miss Weka who was dreadfully allergic to all sorts, but thankfully seems to have mainly outgrown them.
Next door's little boy has an extremely severe allergy to nuts (including a kiss from someone who had eaten a walnut, and being in a room with carrot cake with walnuts on top) and has to have an epi-pen wherever he goes.
Hmm, several ideas, but nothing concrete. Food ingredients now certainly often include things like peanuts, in oil or otherwise.
Mainly I think it's the diversity of food children are now exposed to, and it's often questionable as to what they may contain. Would you have eaten a cashew nut at four? It's just not something many of us would have been exposed to, but if we had, maybe as children we'd have been allergic. Peanuts and peanut butter were not so common either. And we didn't generally eat out, food was very simple, mostly indigenous produce.