Petunia if you are going to look at food intolerances I really recommend doing it thoroughly, scientifically and with the support of a really experienced dietician. There are so many mistakes and pitfalls to make that will lead to false conclusions and you need to make sure you are doing it safely as well as thoroughly. In Australia I recommend the Royal Prince Alfred Hospital Elimination Diet Handbook, their cook book and then a local dietician familiar with their approach. I am not sure what to suggest to you...
For us we followed the handbook recommendations for how to go strictly low salicylate, low amine, no numbers (colours, flavours, preservatives), gluten and dairy free. Once you have been on this elimination stage diet and had two weeks of reduced symptoms you start adding things back in one at at time. If you saw no change on the diet and you are sure you got it right (it's very easy to miss hidden sources), then you can pretty much just go back to normal (but pay attention to see if that causes any issues). If you did see improvement from symptoms and you are going to challenge to see what caused the problem then there are really strict rules about how to do this as there are very few foods that have only one of the chemicals in that you might need to test (for example cheese has both dairy AND amines, many foods have both salicylats AND amines), you need to challenge in high enough doses and over enough days before concluding whether you can or can't re-introduce that food. This is why you need the experienced deitician.
My husband had known dairy issues right from childhood, but was drinking milk, eating cheese and all other sources of dairy like it was going out of style when I made him join the rest of the family on the diet. He would have said he was ok with dairy now. Well after two weeks dairy free he was not and has never since been able to re-introduce dairy without making himself sick. His problem is not with Lactose it's with cow's milk protien. None of my children can tolerate it either, I can tolerate at least some. On the other hand he can eat as much Salicylate as he likes, as can my middle daughther, but my youngest, eldest and I cannot tolerate Salicylate, my youngest daughter's salicylate intolerance is quite extreme.
