Histamine intolerance occurs when there is a buildup of histamine in the body. Many foods contain high histamine levels, and various health conditions and medications can contribute to an intolerance.

Histamine is a chemical that sends messages to the brain, signals the release of stomach acid for digestion, and is released as part of the immune system’s response to an injury or allergic reaction.

An intolerance to this chemical happens when the body cannot break down enough of it in the intestines, causing histamine levels in the blood to rise.

This typically results from having low levels of an enzyme called diamine oxidase (DAO), which is the primary agent that breaks down digested histamine.

Histamine intolerance is relatively rare, affecting about 1–3% of the global population. However, a person or their doctor may not recognize it and may mistake it for a food allergy or gastrointestinal disorder.

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Many foods and drinks contain histamine.

Usually, DAO and, to a lesser extent, an enzyme called histamine-N-methyltransferase(HNMT) break down ingested histamine. But several factors can interfere with how DAO and HNMT work.

When the body does not break down histamine from foods, histamine may leak through the intestinal lining and enter the bloodstream. This can trigger an immune response.

Many prescription drugs can interfere with levels of DAO and HNMT in the body. Some examples of these drugs include:

Meanwhile, over-the-counter and prescription nonsteroidal anti-inflammatory drugs can affect how the body metabolizes histamine. Some examples of these drugs, known as NSAIDs, include:

In addition, high alcohol consumption and health conditions that damage the lining of the gut can lead to histamine intolerance.

A medical professional may have trouble defining and diagnosing histamine intolerance. This may be because the symptoms can arise in many different areas of the body and overlap with those of other conditions.

The symptoms can affect the lungs, skin, and brain, for example, but gastrointestinal symptoms, such as bloating, are most common.

Often, people with histamine intolerance experience:

Less common symptoms include:

Almost all foods and drinks contain some histamine. The amount usually increases as the food ages, spoils, or ferments. Some foods and drinks also contain compounds that help release histamine in the body or block the production or effectiveness of the enzymes DAO and HNMT.

Some foods and drinks that are rich in histamine include:

  • alcohol
  • aged cheeses
  • canned, pickled, and fermented foods, such as sauerkraut
  • smoked products, such as sausage, ham, bacon, or salami
  • spinach
  • eggplant
  • ketchup
  • vinegar
  • canned fish, such as mackerel and tuna

Foods that may trigger the release of histamine include:

  • most citrus fruits
  • cocoa and chocolate
  • tomatoes
  • egg whites
  • fish
  • peanuts

Foods that may interfere with DAO and HNMT levels or actions include:

  • alcohol
  • energy drinks
  • green tea
  • black tea
  • maté tea

Many kinds of bacteria, including common food contaminants, can also produce histamine in the gut. In addition to producing histamine, certain bacteria can affect the health of the intestinal walls. This may lead to intestinal barrier dysfunction in people with histamine intolerance.

If they suspect an intolerance, a doctor may recommend a low histamine diet. Usually, this means limiting the intake of histamine-rich foods rather than excluding them entirely. Studies have found that trying this diet can be important in confirming a diagnosis of the intolerance. It may also improve the symptoms.

However, a person should not have a low histamine diet in the long term unless a doctor recommends it and monitors the person’s health.

Anyone with a low-histamine diet should focus on variety to make sure that they have adequate nutrition.

Foods low in histamine include:

  • fresh meats
  • fresh fish
  • milk substitutes
  • cooked egg yolks
  • most fresh vegetables, except tomatoes and eggplants
  • most fresh fruits, except citrus fruits, strawberries, and cherries
  • fresh, pasteurized milk and milk products

Several vitamins and minerals are necessary for DAO to function properly. Some can even increase DAO activity. For this reason, people with histamine intolerance may benefit from consuming more foods and drinks rich in these nutrients. A person may also benefit from taking these supplements.

Vitamins and minerals that may benefit people with histamine intolerance include:

However, limited laboratory experiments have demonstrated that both vitamins C and B1 can have an inhibiting effect on DAO.

Aside from dietary changes, there is no set treatment for people with histamine intolerance.

However, one or more of the following approaches may help:

  • taking antihistamines
  • taking DAO enzyme supplements
  • avoiding medicines associated with histamine intolerance, which may involve switching medications
  • taking corticosteroids

A 2020 review found that DAO supplementation yielded positive results in the majority of available studies. However, the team called for more rigorous research to establish how effective this supplementation is at treating histamine intolerance.

What are natural antihistamines? Find out here.

Medical professionals often diagnose histamine intolerance after excluding conditions that cause similar symptoms. They may begin by testing for food allergies and intolerances.

For people with chronic intestinal symptoms, a specialist called a gastroenterologist may also test for:

A doctor usually asks anyone who may have histamine intolerance to keep a food diary. This can help them identify symptoms and diet patterns.

They can also check a person’s DAO levels and enzyme activity levels with a blood test.

Many foods contain high histamine levels. If the body is unable to break down this chemical adequately, it can lead to a diverse range of symptoms, which are often gastrointestinal.

Managing a histamine intolerance tends to involve making dietary changes, taking antihistamines or enzyme supplements, and avoiding or limiting the use of medications that trigger the release of histamine.

A diet focused on fresh, minimally processed foods with few preserved or fermented products naturally contains less histamine.