Hi Jack
Your story is familiar to lots of us here. Lots of us have been there. I don't know if it is worth getting very expensive allergy testing done (although it would be interesting) - the main reason is that you may be having a food intolerance.
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www.niaid.nih.gov]
You may like to try the paleolithic diet for a couple of weeks. After a couple of weeks you can start introducing one thing at a time back into your diet. MAke sure you give yourself 24 hours a least before introducing something else and record any reaction - eg stomach cramps, headache, increased heart rate, or even foggy or thick thinking. These are all signs that you are intolerant to what you have introduced. I did this to find out if I was intolerant to anything else after I discovered my body could not handle free glutamate and gave me AF. I have stuck with the basic paleo diet as I was intolerant to them all.
The paleo diet eliminates all food additives including preservatives and flavour enhancers such as MSG, as well as grains (includes rice millet quinoa etc), beans (includes cocoa, coffee as well as string beans) dairy, sugar and potatoes. You can eat all the FRESH meat, fish, and veggies (that don't need to be cooked to be made edible), nuts and eggs (unless you know you are allergic) and fruit you like. You can also use olive oil, coconut oil, lards and drippings etc, and have raw honey maple syrup in moderation - but keep away from vegetable and sunflower type oils, heat treated or pasteurised honey as they are far too processed.
Quite a few on this board are now following this diet as it seems to help them too.
Fran