I just want to add that two other primary "features" of my disorder that have developed over the past few ears are tinnitus and thermoregulation issues.

My tinnitus can range from non-existent to to a high-pitched siren, apparently dependent on my histamine levels.

The thermoregulation problems are particularly problematic. At their worst, I will toggle between freezing cold without explanation to being a hot, sweaty mess. When I discovered I had a large kidney stone last summer, I immediately made major changes to my diet to reduce the amount of oxalates I was eating. In doing so, I inadvertently switched to a high salicylate diet, which sent me into a tailspin. There would be some nights that I wouldn't sleep at all and would flush (aka have a hot flash) every 30 minutes. It was misery until I got a handle on it. The hypothalamus is apparently what's getting hit. Histaminergic Modulation of Body Temperature and Energy Expenditure | IntechOpen

I also have one other clinical finding that may point to histamine as being the issues. On brain MRIs, I have two areas of hyperintensity that are of "unknown clinical significance." Somewhere I came across research reports that indicate this accumulated histamine in the brain shows up as areas of hyperintensity in white matter on MRIs.

Histamine is also associated with wakefulness, so when my histamine levels are high, I just don't sleep. Benadryl does actually help in that state (I buy ones that aren't bright pink since I react to food dyes), but that's not something that should be taken too frequently.

So anyway, I feel like the mystery is slowly unraveling.