I haven't recieved my 23&ME results yet. But, when I was looking at the pfieffer histamine info (a long time ago), I was struck by the fact that, my child didn't fit. Trying to remember, but it seems like she fit the profile behaviorally for high histamine, but, I've always thought she had low histamine because antihistamines really ramp up aggressive/ragey behaviors, her IgE is almost nonexistant, and she has low IgA, IgG4&2. She is compound hetero MTHFR from blood test, and 7.5mg of methylfolate (w/ MB12, and P5P B6) does wonders for her. I have not tested her Ig levels since we've been supplementing w/ the methyls, nor have I tried antihistamines...