Microbial patterns in patients with histamine intolerance.

Histamine intolerance represents a controversially discussed disorder. Besides an impaired degradation of orally supplied histamine due to diamine oxidase (DAO) deficiency, a deranged gut flora may also contribute to elevated histamine levels. Our aim was to determine the intestinal bacterial composition in patients with proven histamine intolerance in comparison to other food intolerances and healthy controls. A total of 64 participants were included in the study, encompassing 8 patients with histamine intolerance (HIT), 25 with food hypersensitivity (FH), 21 with food allergy and 10 healthy controls (HC). All participants underwent blood testing for total and food-specific immunoglobulin E, plasma histamine and DAO serum activity. Stool samples were used to analyze stool histamine and zonulin levels and bacterial composition by 16s rRNA sequencing. No significant differences in stool histamine levels were observed, but HIT patients showed elevated levels of stool zonulin. Microbiota analysis revealed increased levels of Proteobacteria (5.4%) and a significantly reduced alpha-diversity in the HIT group (P = 0.019). On family level, HC showed a significantly higher abundance of Bifidobacteriaceae compared to other study groups (P = 0.005), with lowest levels in the HIT group (P = 0.036). Also significantly reduced abundances of the genera Butyricimonas (P = 0.026) and Hespellia (P = 0.025) were observed in the HIT patients, whereas Roseburia were significantly elevated (P = 0.021). We concluded that the altered occurrence of Proteobacteria and Bifidobacteriaceae, reduced alpha-diversity as well as elevated stool zonulin levels suggest a dysbiosis and intestinal barrier dysfunction in histamine intolerant patients, which in turn may play an important role in driving disease pathogenesis.

Circadian profiling reveals higher histamine plasma levels and lower diamine oxidase serum activities in 24% of patients with suspected histamine intolerance compared to food allergy and controls.

BACKGROUND: Histamine intolerance is thought to trigger manifold clinical symptoms after ingesting histamine-rich food due to reduced activity of diamine oxidase (DAO). No study has hitherto systematically assessed daily fluctuations of histamine levels and DAO activities in symptomatic patients. The aim of the study was to investigate the presence of histamine intolerance, to therefore establish day profiles of histamine levels and DAO activities, and to compare the results between patients with suspected histamine intolerance, food allergy and healthy controls. METHODS: We determined day profiles of histamine plasma levels and DAO serum activities in 33 patients with suspected histamine intolerance, in 21 patients with proven food allergy and in 10 healthy control patients. Clinical symptoms, food intolerances and further clinical and laboratory chemical parameters were evaluated. RESULTS: Twenty-four percent (8 of 33) suspected histamine-intolerant patients showed elevated histamine levels during the day. That might be caused by constantly and significantly reduced DAO activities in these patients compared to food-allergic and control patients. The remaining 25 patients presented normal histamine levels and DAO activities, but an increased prevalence of multiple food intolerances compared to the other subgroup of suspected histamine-intolerants. There was no correlation between subjective complaints and serological histamine parameters in patients with suspected histamine intolerance. CONCLUSIONS: We determined by daily profiling that decreased DAO activities correlated with elevated histamine levels in a subgroup of suspected histamine-intolerants. This finding discriminates these patients from food intolerant individuals with similar clinical symptoms and strongly suggests the presence of histamine intolerance.