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Narrative review discusses link between diamine oxidase deficiency and fibromyalgia pathophysiologyDAO supplementation may reduce fibromyalgia pain and impact

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Key Takeaway
Note the association between DAO deficiency genetic variants and increased symptom severity in fibromyalgia.

This narrative review explores the potential role of histamine intolerance and diamine oxidase (DAO) deficiency in the pathophysiology of fibromyalgia. The authors synthesize evidence regarding the prevalence of genetic variants associated with DAO deficiency, noting a higher prevalence of 74.5% in fibromyalgia patients compared to 66% in the general population (p = 0.014).

The review highlights correlations between symptom severity and the accumulation of these genetic variants. Specifically, the authors note an approximately 7-point increase in the Fibromyalgia Impact Questionnaire (FIQ) per allele. Regarding interventions, the review presents data where DAO supplementation resulted in an 8.4 point decrease on the Pain Catastrophizing Scale, compared to a 2.1 point change in the placebo group. Additionally, the DAO supplementation group showed a 12.3 point improvement in FIQ scores, versus a 4.6 point improvement in the placebo group.

While the evidence suggests that histamine intolerance, mediated by DAO deficiency, may contribute to fibromyalgia in certain subgroups, the review focuses on emerging associations. The authors suggest that these mechanisms may play a role in the disease process, but the clinical implications remain an area for further study.

A review of recent evidence suggests a link between diamine oxidase (DAO) deficiency and fibromyalgia. The review found that certain genetic variants associated with DAO deficiency were more common in people with fibromyalgia compared to the general population. Specifically, having more of these genetic variants was linked to increased symptom severity.

In some cases, taking DAO supplements showed a potential benefit. The review noted that people using DAO supplements experienced a larger decrease in pain catastrophizing and better scores on the Fibromyalgia Impact Questionnaire compared to those taking a placebo. This suggests that histamine intolerance, driven by a lack of the DAO enzyme, might play a role in how fibromyalgia affects certain individuals.

It is important to remember that this is a narrative review of emerging evidence rather than a single new clinical trial. While the findings are interesting, more large scale research is needed to confirm these links and determine how effective supplementation is for the broader fibromyalgia community. You should discuss any changes to your supplement routine with a healthcare professional.

What this means for you:
Genetic DAO deficiency may be linked to fibromyalgia symptoms and could potentially respond to DAO supplementation.

Study Details

Study typeRct
EvidenceLevel 2
PublishedApr 2026
View Original Abstract ↓
BackgroundFibromyalgia 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.MethodsWe 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.ResultsKey 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 
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