Thanks Shroom, I did say you can get tested too, not just go by symptoms but that is a specific histamine test not the ones you mentioned...IWDL do one http://www.iwdl.net/histamine.htm
Yes I suppose for some people their symptoms will be an accurate reflection of their histamine status, but yes it's not very reliable if you are half and half!
Taking folic acid seems to be one way of determining if you are a low or high histamine type. According to Carl Pfeiffer high dose folic acid further stimulates histamine production which has a detrimental effect in histadelics (high histamine types) but not in low histamine types. This is particularly so if you have depression....which will get a lot worse. (from "Optimum Nutrition for the Mind" by Patrick Holford).
So you could experiement with folic acid!