This remains an area of active investigation rather than settled science
Compounding this issue, certain mycotoxins have been shown in animal models to suppress the production of Diamine Oxidase (DAO), the primary enzyme responsible for breaking down dietary histamine in the gut

Cyanocobalamin Injection NDC Package 71288-300-02 Package Information Cyanocobalamin injection is cyanocobalamin is indicated for vitamin B12 deficiencies due to malabsorption which may be associated with the following conditions: Addisonian (pernicious) anemia Gastrointestinal pathology, dysfunction, or surgery, including gluten enteropathy or sprue, small bowel bacteria overgrowth, total or partial gastrectomy Fish tapeworm infestation Malignancy of pancreas or bowel Folic acid deficiencyIt may be possible to treat the underlying disease by surgical correction of anatomic lesions leading to small bowel bacterial overgrowth, expulsion of fish tapeworm, discontinuation of drugs leading to vitamin malabsorption (see Drug/Laboratory Test Interactions), use of a gluten-free diet in nontropical sprue, or administration of antibiotics in tropical sprue
Garcia-RuizCFernndez-ChecaJC
These injections are particularly beneficial if you follow a vegetarian or vegan diet, as B12 is mainly found in animal products
doi: 10.1042/bst20160474 40