Is histamine intolerance a treatable subtype of fibromyalgia? evidence and clinical implications—narrative review

Background Fibromyalgia affects 2%–8% of the global population with suboptimal treatment outcomes. Emerging evidence suggests histamine intolerance, mediated by diamine oxidase (DAO) deficiency, may contribute to fibromyalgia pathophysiology in specific patient subgroups. Methods We conducted a comprehensive narrative review of literature published 2000–2025, examining genetic polymorphisms, biochemical markers, and clinical studies investigating relationships between histamine intolerance, DAO deficiency, and fibromyalgia. Studies included genetic association analyses, randomized controlled trials, and population-based observational research. Results Key findings revealed 74.5% prevalence of DAO deficiency-associated genetic variants in fibromyalgia patients vs. 66% in general population ( p = 0.014), with cumulative variants correlating with increased symptom severity (∼7-point FIQ increase per allele). A randomized controlled trial ( n = 100) demonstrated significant improvements with DAO supplementation: Pain Catastrophizing Scale decreased 8.4 points vs. 2.1 (placebo), and Fibromyalgia Impact Questionnaire improved 12.3 vs. 4.6 points ( p < 0.003). Population studies showed strong associations with histamine-mediated conditions: 29% fibromyalgia prevalence among chronic pruritus patients and odds ratios of 1.30–2.50 for allergic comorbidities among 15,869 fibromyalgia patients. Conclusion Current evidence supports systematic histamine intolerance assessment in fibromyalgia patients presenting with gastrointestinal symptoms, chronic pruritus, or treatment resistance. This review provides a practical clinical framework for identifying and managing this potentially treatable fibromyalgia subtype, though larger multicenter replication studies are needed to confirm findings and establish standardized diagnostic protocols.