Sadly it's quite a new thing - the histamine intolerance thing. I've mentioned it to a few different GPs in relation to some of my symptoms recently and none of them seem to have heard of it. If you google Dr Tina Peers and listen/watch the interviews that come up (some on YouTube, some on the Liz Earle podcast), you'll hear her story - she is a GP and her own daughter had all kinds of symptoms and appeared to have histamine intolerance really badly. Not everyone has such extreme symptoms, but helping her daughter is what led her to research it.
Increasing estrogen also increases histamine, and estrogen also down-regulates the DAO your body produces (which is the enzyme that breaks down histamine), so if you are teetering on the edge of histamine intolerance anyway but pretty symptom-free, adding in estrogen can just push you over the edge...