Are you Histamine Intolerant?
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What Is Histamine Intolerance (HIT)?
Histamine intolerance happens when histamine builds up in the body faster than it can be broken down — most often because of low activity of the enzyme diamine oxidase (DAO). The result can be uncomfortable food-triggered reactions, even though it is not a classic allergy.
Below, we break down what histamine is, what causes histamine intolerance, how to recognize it, and how supporting your DAO levels may help you enjoy the foods you love again.* If you already know dietary histamine is your trigger, you can try Histamine Digest® 30,000 HDU before your next meal.
- Histamine intolerance = histamine builds up faster than your body clears it.
- The DAO enzyme is the body’s main "cleanup crew" for histamine in the gut.*
- Low DAO can come from genetics, age, diet, medications, or gut health.
- Supplemental DAO may help support histamine breakdown at mealtime.*
What Is Histamine?
Histamine is one of many biogenic amines — biochemicals produced through the metabolism of amino acids in all living organisms. It is one of the compounds stored in and released by your mast cells, specialized white blood cells.
When an immune threat, an allergen, or trauma activates these mast cells, they release inflammatory mediators such as histamine. Blood vessels dilate so your white blood cells can carry out the immune defense response. People who have an overabundance of mast cells in their GI tract may also release excess histamine.
Once formed, histamine is either stored or broken down by an enzyme. Research summarized in the American Journal of Clinical Nutrition (Maintz & Novak, 2007; PMID 17490952) identifies diamine oxidase (DAO) as the primary enzyme responsible for breaking down histamine in the digestive tract, preventing it from accumulating and causing overflow.
When your body does not have enough DAO to keep up with the histamine load, you may experience the reactions associated with histamine intolerance.* Supplemental DAO, like the kind in OmneDiem®’s DAO enzyme line, is designed to work right where digestion happens.*
What Causes High Histamine Levels?
What drives such high histamine levels? Sometimes bacterial overgrowth or a compromised gut lining (“leaky gut”) can be the culprit. For people with allergies, the response is driven by an IgE reaction. But for many people with histamine intolerance, it comes down to insufficient DAO enzyme activity — without enough DAO, the digestive system struggles to break down the histamine in the diet.
A comprehensive review, “Histamine Intolerance: The Current State of the Art” (Comas-Basté et al., Biomolecules, 2020; PMC7463562), notes that reduced DAO activity allows dietary histamine to accumulate, leading to a range of reactions. Measuring DAO activity has also been studied as a marker in people with these reactions (Manzotti et al., 2016; PMID 26574488).
Common factors that lower DAO activity
- Genetics: Some people are genetically predisposed to lower DAO production.
- Age: Evidence suggests DAO levels and activity can decline over time.
- Diet: Alcohol and fermented or aged foods are high in histamine and can overwhelm a balanced system.
- Medications: Certain over-the-counter and prescription drugs can block DAO activity.
- Gut health: Because DAO is produced in the gut lining, digestive conditions can reduce its activity.
Think low DAO may be behind your reactions?*
Shop Histamine Digest® 30,000 HDU Compare All DAO SupplementsWhat Reactions Can Histamine Intolerance Cause?
Beyond the familiar skin flushing, histamine rash, runny or stuffy nose, watery eyes, and churning gut, reactions vary widely. Because histamine also influences neurotransmitters, people with low DAO or histamine intolerance may also notice:
- brain fog
- bloating
- wheezing
- eczema
- fatigue, anxiety, and irritability
- hormone imbalances
- low blood pressure
- migraines
- nausea
- racing heart
If these tend to strike after eating high-histamine foods, histamine intolerance or DAO deficiency may be worth discussing with your healthcare provider.
Which Foods Are High in Histamine?
It is hard to predict which foods will cause reactions until you eat them, but these are commonly high in histamine or trigger its release:
- Alcohol — especially wine and Champagne
- Aged cheeses — such as Parmesan
- Cured and smoked meats — bacon, ham, salami
- Canned or salted seafood — sardines, mackerel, tuna, anchovies
- Fermented foods — sauerkraut, kimchi, yogurt, kefir
- Certain produce — tomatoes, spinach, avocado, eggplant, citrus, strawberries
- Leftovers — reheated, aged foods build up histamine
Rather than cutting all of these from your plate, many people choose to support digestion with extra DAO before high-histamine meals.*
How DAO Enzyme Supplements May Help*
Histamine elimination diets can reduce histamine load, but they are difficult to maintain and often only marginally effective. Rather than giving up the foods you love, many people choose to support their digestive DAO levels.*
OmneDiem® Histamine Digest® with DAO (30,000 HDU) supplies diamine oxidase, the enzyme that works in the digestive tract to break down food-derived histamine.* It is not absorbed and does not have systemic activity — meaning it stays in your gut, where it works.* Explore the full DAO Enzyme Supplement collection to compare options:
- Histamine Digest PureMAX — higher-potency DAO for food-related histamine support.*
- Histamine Digest 360 — DAO plus P5P (Vitamin B6) for added mast cell support.*
- Histamine Complete — seasonal and dietary histamine support.*
Frequently Asked Questions About Histamine Intolerance
What is histamine intolerance?
Histamine intolerance is a build-up of histamine in the body caused by reduced activity of the DAO enzyme, which normally breaks histamine down in the digestive tract. It is not a true allergy, but it can cause allergy-like reactions, such as flushing, headaches, congestion, and digestive upset, after eating histamine-rich foods. Histamine Digest® is formulated to supply supplemental DAO.*
What is the difference between a histamine allergy and histamine intolerance?
A classic allergy is an IgE-mediated immune response to a specific allergen. Histamine intolerance, by contrast, results from the body’s inability to break down histamine quickly enough — usually due to low DAO activity — rather than an immune reaction to a single trigger.
What causes low DAO levels?
Common contributors include genetics, aging, high-histamine diets (alcohol, aged and fermented foods), certain medications that block DAO, and gut conditions that affect the intestinal lining where DAO is produced (Comas-Basté et al., 2020).
Can a DAO supplement help with histamine intolerance?
DAO enzyme supplements such as Histamine Digest® supply the enzyme that breaks down food-derived histamine in the digestive tract, which may help support people managing dietary histamine.* They are not a cure and are best used alongside guidance from your healthcare provider.
When should I take a DAO enzyme supplement?
DAO supplements are typically taken shortly before meals that contain histamine, so the enzyme is present in the digestive tract as food is digested.* Follow the directions on your product label.
Is histamine intolerance permanent?
It varies by individual and underlying cause. Some people see changes as they adjust their diet, improve gut health, or change medications. For a personalized assessment, speak with a qualified healthcare provider. You can also review our Common Questions About DAO Enzymes page.
Take the guesswork out of histamine-heavy meals.*
Shop the Full DAO Enzyme Collection