ok, I forgot to mention that if you have histamine problems or even histadelia, then chances are that you are an under-methylating type. I'm sure you will find this in researching, but under-methylation is the explanation for so many mental and physical problems we suffer. Quote I found:

"Much that can go wrong in the human body revolves around the process of methylation which has been mentioned before on this site. Methylation is the process your body uses to make brain chemicals called neurotransmitters which prevent you from becoming depressed and anxious. Methylation helps you to make wholesome DNA which enables you to manufacture healthy new cells. Imperfect methylation can lead to depression, dementia, Alzheimer’s disease, liver disease, ostoearthritis, Parkinson’s disease and even cancer as well as aging. In order to methylate you need a protein called methionine which you can obtain from sunflower seeds, eggs, chicken, turkey, wild game and avocado. Then you need sufficient lashings of vitamins B2, B3, B6, B12, folic acid, a substance called betaine or trimethylglycine, calcium, magnesium and zinc. The way to assess methylation biochemically is to have your homocysteine and histamine levels measured. Ordinarily methionine makes homocysteine which is recycled to methionine care of the appropriate enzymes and the nutrient co-factors mentioned above and normal levels of histamine which is a brain chemical will result. This is what methylation is all about; the recycling of proteins and the donation of what is called methyl groups to make healthy proteins. If homocysteine and histamine are elevated or depressed which can be assessed by means of a blood test then the process of methylation has become dysfunctional which leads to unhealthy proteins and can culminate in autism, depression and schizophrenia."

If you have high histamine avoid folic acid and b12 they raise levels immensely! believe me I know from expereince