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Understanding Histamine, AOC1, and What Your Genotype Means

Histamine is a natural chemical that helps control immune responses, digestion, and brain function. When histamine is released or absorbed faster than it is broken down, it can build up and cause symptoms that feel like allergies, such as headaches, flushing, hives, nasal congestion, bloating, or other digestive discomfort.

The AOC1 gene provides instructions for making the enzyme diamine oxidase or DAO. DAO is the main enzyme responsible for breaking down histamine in the digestive tract. Differences in the AOC1 gene can change DAO activity. Lower DAO activity means histamine from food and internal sources can accumulate more easily, raising the risk of histamine-related symptoms. Higher DAO activity helps keep histamine levels balanced.

How to Think About Your Genetic Result

Your rs1049793 genotype affects likely DAO activity and your relative odds of histamine intolerance. The following accordion explains typical interpretations for each genotype and what that could mean in daily life. Use these explanations to guide conversations with your healthcare provider. PlexusDx does not provide medical advice. Always consult your healthcare provider before making changes to diet, supplements, or medications.

Two effect alleles (GG) — Reduced DAO activity, higher odds of histamine intolerance

With the GG genotype you carry two copies of the effect allele associated with lower DAO activity. This typically means your body may produce less active DAO enzyme and be less efficient at breaking down histamine in the gut. As a result, histamine from foods or produced internally can build up more easily, increasing the likelihood of symptoms like:

  • Bloating, abdominal discomfort, or changes in bowel habits
  • Headaches or migraine-like pain
  • Hives, flushing, or itchy skin
  • Nasal congestion or sinus symptoms resembling allergies

Practical considerations: If you notice recurring symptoms after meals, consider keeping a food and symptom diary, testing for DAO activity or blood histamine levels with your clinician, and working with a provider or dietitian experienced in histamine intolerance management.

One effect allele (CG) — Slightly reduced DAO activity, moderate odds of histamine intolerance

The CG genotype means you carry one effect allele. This is associated with a modest reduction in DAO activity. You may process dietary histamine reasonably well most of the time, but under certain circumstances — large histamine loads, stress, illness, medications that block DAO, or gut disturbances — histamine can accumulate and produce symptoms similar to those above.

Practical considerations: Monitoring trigger foods and timing, limiting high-histamine meals in stressful periods, and discussing targeted testing with your clinician can help determine whether dietary or supplemental strategies are useful for you.

No effect alleles (CC) — Higher DAO activity, lower odds of histamine intolerance

With the CC genotype you carry two copies of the non-effect allele, generally associated with better DAO activity and a lower risk of histamine-related symptoms. You are genetically better equipped to break down histamine in the gut. That does not eliminate the possibility of histamine reactions entirely, because other factors such as medications, gut health, or very histamine-rich meals can still overwhelm DAO capacity.

Practical considerations: If you have symptoms despite the CC genotype, work with your healthcare provider to explore non-genetic causes such as gut disorders, mast cell activation, or medication effects.

Diet Recommendations to Support Healthy Histamine Balance

  • Focus on fresh, minimally processed foods. Fresh meats, freshly caught fish consumed promptly, fresh fruits and vegetables (except high-histamine or histamine-releasing items listed below), eggs, and whole grains are generally lower in histamine than aged or fermented foods.
  • Avoid or limit high-histamine foods: aged cheeses, fermented foods (yogurt, sauerkraut, kimchi, kombucha), processed or cured meats, shellfish, smoked fish, and alcoholic beverages, especially wine and beer.
  • Avoid leftovers if you are sensitive. Bacterial action during storage increases histamine in foods; eating freshly prepared meals reduces exposure.
  • Be cautious with certain fruits and vegetables that can trigger histamine release in sensitive people, including tomatoes, spinach, eggplant, strawberries, and avocados. Individual triggers vary.
  • Include foods rich in vitamin B6 and vitamin C since these nutrients support DAO activity and histamine metabolism. Examples: bell peppers, citrus fruits, strawberries, broccoli, sweet potatoes, bananas, chickpeas, potatoes, and liver (if tolerated).

Supplement Considerations

  • Vitamin B6 and vitamin C supplements can support histamine breakdown. Discuss dose and suitability with your healthcare provider before starting supplements.
  • DAO enzyme supplements are available and sometimes used before meals to help metabolize dietary histamine. Effectiveness varies and your clinician can advise whether a trial is reasonable for you.
  • Be cautious with broad-use probiotics. Some probiotic strains produce histamine while others do not. Speak with a clinician or dietitian about strain-specific options if you are considering probiotics.

Lifestyle and Other Practical Tips

  • Manage stress. Stress can increase histamine release and reduce digestive enzyme function. Practices such as regular sleep, relaxation techniques, and mindfulness can help.
  • Prioritize sleep. Poor sleep impairs overall metabolism and immune balance and can make histamine symptoms worse.
  • Stay active. Regular moderate exercise supports digestion and metabolic health. Avoid intense exercise immediately after large, histamine-rich meals if you are sensitive.
  • Review medications. Some medicines and supplements can inhibit DAO or increase histamine release. Always review prescriptions, over-the-counter drugs, and supplements with your clinician.
  • Support gut health. Conditions that damage the intestinal lining or alter gut bacteria can reduce DAO activity. Work with your healthcare provider to evaluate and treat underlying gut issues when appropriate.

Testing, Monitoring, and When to Talk to a Clinician

  • Keep a simple food and symptom diary to help identify patterns between what you eat and how you feel.
  • Discuss laboratory testing options with your provider. Tests may include serum DAO activity, blood histamine levels, or broader evaluations for food sensitivities, celiac disease, or gastrointestinal disorders if symptoms are persistent.
  • If symptoms are occasional and mild, dietary adjustments and supportive nutrients may be enough. For frequent or severe symptoms, seek evaluation to rule out other causes such as mast cell disorders, allergies, or gastrointestinal disease.

Important Disclaimer

PlexusDx provides educational information about genetic predispositions only. This content does not constitute medical advice. Always consult your healthcare provider before making changes to your diet, starting or stopping supplements, or changing medications. Your healthcare provider can interpret genetic findings in the context of your overall health, symptoms, and clinical tests.