Dear Finn, its such a trial and error thing isnt it. When I first became ill I could eat something and get the most terrible reactions from it, rashes, vomiting, all kinds of things, then I could eat the same the the next day and feel fine. My Mercury hair test showed up as 0 so Im still not sure this is my problem. Certainly if your not absorbing vitamin B12 this can cause many physical and mental symptoms, including allergies. This is why Ive decided to start from scratch and look into everything. Ive been lucky so far in finding out that I dont absorb B12 and will have to have shots for the rest of my life. My GP is doing a Candida test and many others and I have an appointment with Dr Peatfield soon to sort out my thyroid and Adrenal stuff. Best of luck Tracy x PS if you are someone who dosent absorb B12, this can be genetic and taking it orally wont work.