Diamine oxidase, or DAO, is an enzyme found in your small intestine that helps break down histamines from the food you eat. Histamines are prevalent in aged cheeses, cured meats, alcohol, spinach, and more. For most people, DAO does an excellent job of keeping histamine levels in balance.
However, some individuals have an over- or under-production of DAO, leading to histamine intolerance. The goal of this article is to help you understand how DAO impacts your health, symptoms of imbalances, and effective ways to supplement or manage histamine intolerance.
Understanding Histamine and Histamine Intolerance
Histamine is a natural compound found in many foods and produced by your body’s immune system. In small amounts, histamine helps regulate immune responses, digestion, sleep, and more.
However, histamine is released by mast cells, which are part of your immune system. When there is an allergic reaction or inflammation, mast cells release a flood of histamine. While this is meant to protect you, too much histamine can lead to problems.
Histamine intolerance, also known as histaminosis, refers to an impaired ability to break down histamines properly. It affects about 10% of people and causes unpleasant symptoms like hives, itching, diarrhea, fatigue, and dizziness after eating high-histamine foods.
These symptoms are not the result of a true allergy, however. You may be sensitive to histamines, but not strictly allergic. The key difference is an allergy involves an immune response, whereas histamine intolerance is due to limited DAO enzyme activity.
Causes and Risk Factors for Histamine Intolerance
The primary cause is a shortage of diamine oxidase enzyme, which can occur due to:
Genetic mutations or polymorphisms: Certain variants of the gene for DAO can reduce enzyme activity or production. If you inherited one of these variants, it may make you more prone to histamine intolerance.
Gastrointestinal issues: Conditions like ulcerative colitis, Crohn’s disease, SIBO (small intestinal bacterial overgrowth), and celiac disease can damage the small intestine where DAO is produced, leading to deficiency.
Bacterial overgrowth: An overgrowth of bacteria in the small intestine can consume available nutrients and oxygen, crowding out DAO production. Antibiotics further reduce gut bacteria and may trigger symptoms.
Other factors that may increase risk include:
- Age over 50: As we get older, DAO production and activity naturally start to decrease a bit.
- Smoking: Smoking interferes with DAO activity and absorption of nutrients needed to produce it.
- Medications: Certain medications like antibiotics, ulcer medications, and blood pressure medications can deplete nutrients or damage gut lining.
Impaired Histamine Degradation
Aldehyde dehydrogenase deficiency: ALDH enzymes help convert histamines into less reactive metabolites that are easier to excrete. A deficiency in certain ALDH enzymes, especially ALDH2, can lead to a buildup of harmful histamine metabolites that cause symptoms. Supplementing with NADH or riboflavin (cofactors for ALDH enzymes) may help boost activity.
Enteral histaminosis: This term refers to poor degradation of histamines in the small intestine specifically. It’s often seen in people with SIBO, ulcerative colitis, celiac disease or Crohn’s disease – any condition that damages the lining of the small intestine.
Since the small intestine is responsible for breaking down a large portion of histamines from food, damage to this area leads to elevated histamine levels that cause symptoms.
Treatment focuses on managing underlying conditions through diet, probiotics, antibiotics or other therapies to restore health and proper histamine digestion.
Exogenous Histamine Sources
Histamine-rich foods: Foods high in histamines include aged cheeses, cured meats, pickled foods, soy products, spinach, organ meats, nuts, and grain fibers. While healthy in moderation, these can trigger symptoms in those with intolerance. It’s best to limit or avoid them.
Artificial additives: Preservatives like sodium nitrite (used on meats), sulfites (used on wines and dried fruits), MSG, and sweeteners like aspartame may release histamine. Even natural flavors can harbor histamines. Check labels and minimize additives when possible.
Ingesting histamine supplements: Unfortunately, some supplements like histidine, L-histidine, and histamine phosphate contain free histamines that exacerbate symptoms. It’s best to avoid supplements with histamine or its precursors if you have intolerance.
The severity of symptoms depends on the form, dose and deficiency of DAO – an imbalance of intake versus breakdown. The most effective approach is reducing excess histamine sources while enhancing your ability to digest the histamines you do consume through supplementation, probiotics, digestive enzymes or managing other gut issues.
Diagnosis and Assessment of Histamine Intolerance
Histamine challenge test: After an elimination diet, small amounts of common triggers are reintroduced one by one to see your reaction. This helps pinpoint specific triggers to avoid. However, the test may provoke symptoms, so you need to weigh the benefits versus risks.
Blood tests
- Diamine oxidase activity: A DAO test measures how well your DAO breaks down histamines. Lower than normal suggests deficiency.
- Urinary histamine metabolites: Elevated levels indicate impaired breakdown and intolerance.
- Cytokine levels: High levels of inflammatory cytokines TNF-alpha and IL-6 may point to a hypersensitivity response versus true intolerance.
Elimination diet
Remove histamine triggers for 4-6 weeks to allow symptoms to subside. Then reintroduce foods one by one to find which cause a reaction. This allows you to practice management strategies.
Consulting a doctor
See an allergist, gastroenterologist or family physician who is knowledgeable about histamine intolerance. They can properly evaluate your condition, run diagnostic tests and determine if an underlying issue like ulcerative colitis or SIBO may be present and need treatment. They can also recommend tailored management approaches and treatment plans.
Effective Ways To Treat and Manage Histamine Intolerance
Dietary strategies
Low-histamine diet: Avoid high-histamine foods like aged cheeses, cured meats, pickled foods, spinach, nuts and smoked/processed meats. Focus on fresh fruits and vegetables, cooked meats, rice, oats and legumes until symptoms subside.
Restrict triggers: Identify specific high-histamine foods that trigger your symptoms and avoid them altogether. You may need to cut many triggers or just a few, depending on severity. Gradually reintroduce to assess tolerance.
Practice good habits:
- Eat multiple small meals spread throughout the day versus large meals. This stabilizes blood sugar and histamine levels.
- Stay hydrated. Proper hydration aids digestion and flushing toxins from your body.
- Cook meats, eggs and leafy greens thoroughly to destroy less stable forms of histamine.
- Consume probiotic foods or supplements to improve gut health and digestion.
While dietary strategies form the foundation, other treatments you may want to consider include:
- DAO supplements: Can aid symptoms and prevent recurrence if avoidance alone is not enough. Look for enteric-coated capsules for absorption.
- Digestive enzymes: Help improve digestion and limit substrates available for excess histamine production. Works best with carbohydrate and protein splitting enzymes.
- Allergy testing: If symptoms seem out of proportion or last throughout the year, allergy testing may reveal sensitivities to be addressed. Treatment would include allergy shots or other immunotherapy.
Gastroenterologist: For underlying conditions or severe symptoms, see a gastroenterologist. They can determine if SIBO, H. pylori infection, irritable bowel syndrome or another issue may need treatment like antibiotics or other medications. Treatment will aim to reduce inflammation and restore balance.
Diamine oxidase enzyme (DAO) supplements
- Helps boost low DAO activity and support digestion of excess histamines.
- Look for enteric-coated capsules as these survive stomach acid and release in the small intestine where DAO is most active.
- Typical dosage is 50-150 mg, 2-3 times per day.
- Popular brands include NOW Foods DAO Enzyme, Zenwise Health DAO Enzyme and Seeking Health DAO Enzyme.
Digestive enzymes and support
| Proteolytic enzymes | Help break down excess histidine, one of the amino acids that produces histamines. Papain and bromelain are popular options. |
| Carbohydrate enzymes | Limit substrate for histamine production. Look for amylase and amyloglucosidase. |
| Probiotics | Improve gut health, balance bacteria and support digestion. Look for strains like L. acidophilus, L. plantarum, B. lactis and S. thermophilus. |
| Betaine HCL | Helps increase stomach acid, which in turn supports enzyme production and absorption. Low stomach acid is linked to lower DAO. |
| Peppermint or Ginger | Natural anti-inflammatories that can soothe the gut lining and improve digestion. Available in tea, capsule or liquid extract form. |
| Glutamine | An amino acid that helps maintain the health and integrity of the gut lining. Can aid conditions where excess histamine may leak from the gut into the bloodstream. |
| Turmeric or Curcumin | The curcumin in turmeric has potent anti-inflammatory effects. Can help reduce excess histamine responses and support gut health. |
Lifestyle modifications
Stress reduction: Chronic stress causes inflammation and imbalance in the body. Practice relaxation techniques like yoga, meditation, deep breathing or journaling daily.
Exercise and sleep
Moderate exercise improves digestion and immunity but intense workouts can increase sensitivity. Aim for 30-60 minutes of walking, yoga or gentle cycling most days.
Sleep helps your body regulate inflammation and heal. Aim for 7 to 8 hours of sleep per night to allow your body’s systems to rebalance.
Allergic response management
While histamine intolerance is not an allergy, excess histamines can trigger an inflammatory response that resembles allergy symptoms like congestion or rashes. Some tips to help manage these responses:
Nasal corticosteroid sprays: Can help reduce post nasal drip and congestion. Use as directed under guidance of your doctor.
OTC antihistamines: Oral antihistamines like Zyrtec, Claritin or Allegra can help with symptoms of excess histamine release but will not treat the underlying intolerance. Only use short-term and as directed.
Rash creams with corticosteroids: Over-the-counter hydrocortisone cream can help reduce inflammation, redness and itching from excess histamine release. Use as directed to avoid skin thinning.
Cool compresses, aloe vera and calamine lotion: Can provide soothing relief from rashes, itching and irritation. Apply as often as needed to promote comfort.
Nettle tea: Stinging nettle has natural anti-inflammatory and antihistamine-like effects. Drink 1-3 cups per day to help reduce symptoms. Be sure to steep properly as leaves can cause a stinging rash if not.
Important factors to consider when choosing a reputable DAO supplement
Product quality and effectiveness:
Enzyme activity (units) and potency: The higher the units and potency, the more active the enzymes are at breaking down excess histamines. Look for at least 3000-5000 units per capsule for histamine intolerance.
Pure, natural and additive-free: The best supplements use high-quality whole food extracts or coenzymes to produce the enzymes naturally. Avoid fillers, binders, dyes and GMOs.
Scientific studies: Reputable brands will have research studies showing the effectiveness of their DAO extract or specific strain for reducing histamine levels and supporting digestion. Clinical trials are most rigorous but case studies and pilot studies also provide useful evidence.
Supplement forms
Capsules and tablets: The most common and convenient form. Look for enteric-coated capsules that can survive stomach acid for release in the small intestine.
Food supplements: Powders, liquids and syrups provide flexible dosing but may be unpleasant for some. Look for a natural fruit flavoring without dyes or sweeteners when possible.
Fortified foods: Some cereals, protein bars, nut butters or vegan protein powders contain added DAO enzymes. Carefully check nutrition labels to ensure the potency and purity meets your needs. Fortified foods may be more appealing but often do not contain as high an amount or potent enzyme per serving compared to supplements.
The most effective DAO supplements will have high-quality, natural ingredients; solid research and evidence backing their effectiveness; formulated specifically for histamine intolerance or digestive support; and produced by a reputable brand that prioritizes purity, potency and safety.
Where to Buy Diamine Oxidase Enzyme (DAO)
Online retailers
| Amazon | Large selection, competitive pricing and reviews, often eligible for Prime shipping. |
| iHerb | More specialized in supplements and vitamins with lower prices for many products. Offers coupon codes frequently. |
| Vitacost | Sells their own line of supplement brands as well as many popular national brands. Often has sales and discounts on select products. Prices are not always the lowest but selection is quite good. |
Local health food stores and pharmacies
- Gives you an opportunity for in-person consultation with staff to find a high-quality DAO supplement that meets your specific needs.
- Can assess dosage and product options on the spot versus guessing based on limited information online.
- Supports a local small business in your community.
Factors to consider when purchasing
Price comparison across sites to ensure you’re getting the best available deal for the product that suits you best. Prices may vary significantly for the same supplement.
Check customer reviews to compare product experience, effectiveness and any side effects or issues reported. Look for mostly positive reviews mentioning reduced histamine symptoms or digestive support.
Speaking with a doctor or nutritionist is the best way to determine if DAO supplementation is appropriate and the best product for your unique condition and needs. They can evaluate your symptoms, diagnosis, medications and lifestyle to provide personalized guidance.
Overall, with some research comparing options, you can feel confident purchasing DAO supplements online or locally to support your histamine intolerance management and digestive health.
The most important things are choosing a high-quality, effective product, getting the dosage and form that suits you best, and using it properly under guidance as recommended by your healthcare team.
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