We've been there done that and it is so hard trying to analyse what could be an allergy trigger when there are so many variables.
We were given a recipe book which we used to duplicate a lot of favourite foods but without the colouring, preservatives or other problem triggers. For example, we no longer buy popcorn except in pure kernel form, to be popped in a hot air popper. We don't add the commercial popcorn salt because it is coloured, loaded with preservatives and artificial flavours. Instead, we add butter (plain butter, not the dairy whip kind, with loads of other stuff) and pure salt. It's a special treat to sit and eat freshly popped popcorn while we watch DVDs together.
We also found suppliers of 'home-made' type foods where there were no additives, just the raw ingredients (very few of them). Blocks of honeycomb, for example - nothing but sugar and bicarb soda. The allergy clinic also gave us a list of 'safe' brands to use. Even commercial lemonade was off the list, except for one generic brand.
We were told that difficult child 3 had to be stable on the diet for several weeks before we could try introducing 'challenge' foods. If difficult child 3 broke the diet or developed a reaction, we clock got re-set and we went back to start. He quickly learned that this unpleasant diet would end fastest if he cooperated. It wasn't fault-based - if he snuck food and reacted, the clock got re-set. If a food we carefully introduced produced a reaction, the clock got re-set. If we introduced a new food at the same time as he cheated on his diet, and he got a reaction - he was told that now we didn't know which food had caused the reaction and we would have to do it all again, we had now lost twice the lead-up time because we not only had to re-set, we had to re-test each suspect food individually.
Soon he was diligent about reading food labels.
This can be so tricky because often this isn't just a typical allergy, it's also a matter of levels. Example: difficult child 3 is allergic to the artificial colour brilliant Scarlet. If he takes medicine coloured with this, he gets a big allergy reaction, body and face covered with hives. If he eats ONE sweet coloured with this, he MAY get a milder reaction. If he eats another sweet coloured with this in the next week he will get a bigger reaction. If he's been 'clear' of this colouring for months and eats one small sweet, maybe no reaction. But that one sweet will have raised his levels and re-sensitised him, so even a tiny dose within a few days can be enough to trigger another reaction.
Or a different allergy could be more sensitive, because his immune system is already on alert.
Trying to sort this out is difficult enough, when you have a child who is cooperating. Accidents will still happen, he will forget, I will forget, someone else will forget. We also found that difficult child 3 was OK with nuts, in fact it was one of the few foods he could have. But he wasn't allowed to take ANY nut butters to school, so we really had difficulties finding food he could eat at school. No school lunches, it all had to come from home. We also had to choose foods which didn't need refrigeration - which almost begs for preservatives, or the kid goes hungry. When your child's lunchbox is sitting in his bag with an Aussie summer sun incubating it all morning, there's not much viable food can stand up to this. Forget the chicken sandwiches. It's no wonder Aussie kids are so loaded with preservatives that when we die, they don't bury us, they put us out for recycling.
Don't worry too much about what these people think - the more you communicate (effectively) the less you need to write a novel and the more they get to know you. Don't force it, just do what you have to do.
Setting up a meeting ASAP will also fast-track this process. And as I suggested before - the Book. It really does make life easier, for you AND the teachers. It gives you a much faster information turnaround time than emails. It also gives you ALL a chance to read back through the book and sometimes see a pattern that emails don't always show, because with emails you don't usually see them all side by side.
It's early days. They already know you have genuine concerns - you're not imagining any of this. They also already know that you are on to this, you are not fooled by your kid.
Marg