Everything about histamine intolerance & how to handle it!

As allergy season arrives, you may experience familiar symptoms such as sneezing, itchy eyes, and a runny nose. While these are often caused by seasonal allergies, like hay fever, some people experience similar symptoms throughout the year due to histamine intolerance.

Although hay fever and histamine intolerance can look alike, they are not the same condition. Hay fever is an immune response to allergens such as pollen or pet dander, whereas histamine intolerance occurs when the body cannot break down histamine efficiently, allowing it to build up over time.

In this guide, we’ll explain what histamine is, why it’s essential for good health, what causes histamine intolerance, the symptoms to look out for, and practical ways to support healthy histamine balance through diet and gut health.

What is histamine?

Histamine is a naturally occurring chemical produced by both your body and certain gut bacteria. It plays an essential role in many everyday functions, including:

Supporting your immune system
Regulating stomach acid production
Acting as a neurotransmitter in the brain
Controlling the widening and narrowing of blood vessels
Helping your body respond to injury and infection
Initiates inflammation and other immune system reactions when the body is exposed to harmful pathogens or irritants¹

Most histamine is stored inside specialised immune cells called mast cells, which are found in the skin, digestive tract, lungs and other tissues exposed to the outside world.

Histamine is also present in many foods, particularly fermented foods, where bacteria naturally produce it during fermentation.

Hay fever Vs histamine intolerance

Many people confuse hay fever with histamine intolerance because the symptoms overlap.

Hay fever

Hay fever occurs when your immune system mistakenly identifies harmless substances such as pollen or pet dander as dangerous. This triggers the production of IgE antibodies, causing mast cells to release histamine and other inflammatory chemicals. The result is symptoms such as:

Sneezing
Runny nose
Blocked nose
Watery eyes
Itchy eyes and throat

Histamine intolerance

Histamine intolerance (HIT) is different. Instead of producing too much histamine in response to an allergen, the body struggles to break histamine down effectively. This allows histamine to accumulate, leading to symptoms that may affect multiple body systems.

Common symptoms include:²³

Headaches and migraines
Flushing
Itching
Hives (urticaria)
Eczema/psoriasis
Weight loss
Nasal congestion
Runny nose
Diarrhoea
Nausea
Abdominal pain
Dizziness
Fatigue
Low or high blood pressure
Anxiety

These symptoms often fluctuate depending on diet, stress, gut health and overall histamine load.

What causes histamine intolerance?

1. Reduced DAO enzyme activity

The enzyme diamine oxidase (DAO) is responsible for breaking down histamine in the digestive tract. If DAO production is reduced or its activity is impaired, histamine levels can rise, causing symptoms listed above.⁴

Reduced DAO activity may result from:⁵

Genetics
Certain medications
Gut inflammation
Damage to the intestinal lining
Changes in the gut microbiome

2. Gut dysbiosis

An imbalance of gut bacteria can influence how much histamine is produced and broken down.

Low levels of bacteria that produce the enzyme, DAO, to assist in the breakdown of histamine (Lactobacillus rhamnosus, Bifidobacterium infantis, Bifidobacterium longum, Lactobacillus plantarum, Lactobacillus reuteri).
High levels of histamine-secreting bacteria (eg Staphylococcus, Proteus, Clostridium perfringens, and Enterococcus faecalis).⁶

3. Eating large amounts of high-histamine foods

Remember, bacteria produce histamine, so fermented foods are high on the list here:⁷

Kefir
Yoghurt
Sauerkraut
Kimchi
Miso
Tempeh
Wine and beer
Salami
Tuna
Sardines
Mackerel
Shellfish

4. Histamine-releasing foods

Some foods don’t contain high levels of histamine but encourage mast cells to release it, including:⁸

Citrus fruits
Tomatoes
Spinach
Cocoa
Cashews
Walnuts
Peanuts

5. Certain medications

Some medicines reduce DAO activity or interfere with histamine metabolism. Always speak with your GP or specialist before changing prescribed medication.

How to restore balance & support healthy histamine levels

Avoiding high-histamine foods may reduce symptoms temporarily, but it doesn’t address the underlying causes. Try:

Work out your personal quota for eating histamine-rich foods.⁹This may take a bit of trial and error. Until your gut health improves and you’re able to tolerate more foods, keep a journal to track your intake of histamine-rich foods and how they affect you. As you progress along your gut health journey, you’ll be able to see the improvements!

Support a diverse and balanced gut microbiome by following a gut-healthy diet. Histamine intolerance is primarily a gut issue as both the enzymes and bacteria that break down histamine are all located in the gut.¹⁰

Support a healthy gut lining and the creation of the protective mucus layer with a diet rich in fibre and polyphenols.¹¹ Consider taking a collagen supplement, which will help reduce inflammation and promote gut healing. The better the integrity of the gut, the lower the chance of developing histamine intolerance. Note that collagen and bone broth can both activate mast cells in the gut to produce histamine, however, the trick is to reduce the amount of collagen to a level that you can tolerate.

Feed the butyrate-producing bacteria in your gut (e.g. Faecalibacterium and Roseburia) with plenty of fibre. Butyrate helps dampen down mast cell activation, reducing the release of histamine. Include a variety of pulses, legumes, whole grains, fruit and vegetables, and nuts and seeds.¹² Remember to drink plenty of water alongside fibre to avoid constipation, and if you are currently on a low-fibre diet, introduce fibre slowly to avoid digestive upset such as flatulence and bloating.

Ensure regular bowel movements. Constipation may cause a build-up of histamine in the colon which can then be reabsorbed into the bloodstream. For a step-by-step guide to combatting constipation, read this article.

Stress management. Stress can increase histamine release while also disrupting the gut microbiome. Activities such as walking, mindfulness, yoga and breathing exercises may help reduce overall histamine load.

Is kefir suitable for histamine intolerance?

Although some probiotic bacteria in kefir naturally produce histamine, research also suggests kefir may help support gut health and reduce mast cell activation through the production of beneficial compounds, such as butyrate.¹³¹⁴

If you have histamine intolerance, it’s usually best to introduce kefir slowly. Many people begin with one tablespoon per day and gradually increase the amount as tolerated. If you begin experiencing ‘detox’ symptoms (a worsening of existing conditions), we recommend cutting down to just one teaspoon and building up slowly again.

As always, everyone’s tolerance is different. Our team of Nutritional Therapists are here to guide and support you every step of the way. Get in touch for free advice via live chat, weekdays from 8am to 8pm 😊

Histamine is essential for many important functions throughout the body, but when it builds up faster than it can be broken down, it may contribute to a wide range of symptoms.

Rather than focusing solely on avoiding histamine-rich foods, supporting your gut health, microbiome diversity, digestive function and stress levels may provide a more sustainable approach to improving histamine tolerance over time.

If you have persistent symptoms or are being treated for allergies or histamine intolerance, consult your GP, immunologist or registered healthcare professional before making significant dietary changes.

If you’d like to find out more about food sensitivities, read Food allergies, sensitivities and intolerances – what is the difference?

Any questions? Contact one of our Nutritional Therapists via live chat, we’re available on weekdays from 8am to 8pm.