https://www.reddit.com/r/HistamineIntolerance/comments/ytmcl4/comment/iw75m9l/Quote:
Hi-dose
NaturDAO (specifically that brand of plant-based histamine enzyme; OTC antihistamines had virtually zero effect on me). Regimen is 5 to 10 pills a day. I take on AM, PM, 5 minutes before meals, and anytime I feel super crummy. For initial testing, take one pill and wait 24 hours to ensure no side effects for you personally, then do hi-dose for 3 days (72 hours to allow inflammation to go down) to see if it helps at all. You should know within a week if it helps or not! Needs to be coupled with the next two steps below for maximum effectiveness.
Primarily low-histamine diet. I can tolerate hi-histamine foods once in awhile.
LOTS of sleep, including naps. The effect of the enzyme pills is greatly amplified by copious amounts of sleep
Key question for "subset HIT" (especially if you don't respond to antihistamines)