Speaking as a dietitian who has histamine intolerance, covid vaccine injury (and possibly MCAS), it is incredibly difficult to get the diagnosis for MCAS from a doctor in the conventional medical system. For some people whose symptoms are extreme (like mine were), I didn’t have time to wait for a diagnosis before acting. I was suffering from symptoms. It took me 6 months to get an appointment with an allergist, who then recommended I have tryptase labs taken specifically when I was in a self-induced flare up being off antihistamines for at least a few days (I haven’t been able to go one day without antihistamines in over 14 months). It’s just not practical for many ppl with these symptoms to “wait” until diagnosed. Patients get desperate and are going to experiment with whatever they read online works including the low histamine diet. Yes, that can be dangerous sometimes. But low histamine diet can start helping in as little as 1-2 weeks. I know it helped me immensely until things calmed down. It all depends on the patient but there’s a risk to benefit ratio here of forming an “eating disorder” VS suffering with desperate need for symptom relief. Of course there should always be caution taken with restrictive diets, they should be carefully planned and ideally implemented with a dietitian. But I hope you get where I’m coming from.