All you need to know about histamine intolerance

histamine intolerance blog image - itchy leg

What is histamine?

Histamine is a chemical produced in cells throughout the body as part of the body’s inflammatory response to allergy, infection, or injury. In short, it sends red flag messages to your immune system, notifying your white blood cells to rally up against potential attackers that may be infecting your tissues.

As well as being an important part of your body’s immune response, histamine also plays a key role in digestion by aiding in the production of stomach acid, as well as regulating sleep.

When damaged or exposed to allergens, cells in the skin, nose, throat and lungs release histamine, resulting in pain, itchiness, redness, runny nose, and wheezing.

Histamine causes your blood vessels to swell so that your white blood cells can quickly move in to resolve any problems. It’s part of the body’s natural immune response.

What is histamine intolerance?

Typically, enzymes will break down the histamine so that it doesn’t build up. However, if your body doesn’t break down histamine properly, it builds up and up, and you develop histamine overload and intolerance.

As histamine travels throughout your bloodstream, it can affect your gut, lungs, skin, brain, and your entire cardiovascular system.

Despite the name, histamine intolerance is not an ‘intolerance’ to histamine. Rather, histamine intolerance occurs when you have too much histamine than your body is able to effectively break down.

Histamine intolerance and food allergies

Histamine intolerance is not an allergy. However, it is often difficult to distinguish between the two conditions precisely because the symptoms occur after food consumption in both cases and are virtually identical.

This makes it all the more important to clearly distinguish the two conditions.  Of course it can also be the case that you suffer from a food allergy as well as from histamine intolerance – however, different foods are usually responsible for the respective reactions.  

With histamine intolerance, symptoms can be triggered by certain foods, but the mechanism is different than a food allergy. In the case of a food allergy, symptoms can be almost immediate and that’s why people often need to carry an Epi-pen with them that contains epinephrine to quickly reverse the unpleasant effects of an allergy, in particular helping to open airways into the lungs.

Histamine intolerance is thought to be due to a cumulative build-up of histamine rather than an over-release of histamine. Because of this, the symptoms may not be immediate.  Symptoms may be triggered any time your ‘threshold’ is reached and it may be difficult to pinpoint a particular food as the culprit.

For example, you may have consumed histamine-rich foods in the morning and in the afternoon consumed a low histamine meal. But, the afternoon food was enough to put you over your level of tolerance, so symptoms would occur in the afternoon. You would think your symptoms were due to the afternoon food but in reality, your morning foods were a more important factor.

Symptoms of histamine intolerance

The symptoms of histamine intolerance are similar to those of an allergy, and can include any of the following:

Woman with head due to histamine intolerance
  • Abdominal cramps
  • Abnormal menstrual cycle
  • Anxiety
  • Arrhythmia, or accelerated heart rate
  • Difficulty falling asleep
  • Difficulty regulating body temperature
  • Fatigue
  • Flushing
  • Headaches/migraines
  • Hives
  • Hypertension
  • Nasal congestion, sneezing, difficulty breathing
  • Nausea, vomiting
  • Tissue swelling
  • Vertigo or dizziness

The two major enzymes in the human body that reduce histamine are HMT and DAO. HMT works with histamine in our central nervous system while DAO works to break down histamine in the foods we consume. The most common cause of additional histamine is the failure of DAO to do its job.

Though both enzymes play an important role in histamine break down, DAO is the main enzyme responsible for breaking down ingested histamine. If you’re deficient in DAO, you likely have symptoms of histamine intolerance.

In addition to the histamine produced inside your body, there are also a variety of foods that naturally contain histamine, cause the release of histamine, or block the enzyme DAO that breaks down histamine, each of which can cause a build up of histamine.

What causes high histamine levels?

  • Allergies (IgE reactions)
  • Small Intestinal Bacterial Overgrowth (SIBO)
  • DAO deficiency
  • Excess of histamine-rich foods (see list below)
  • Leaky gut

What causes low DAO enzyme status?

  • SIBO– the bacteria in SIBO can degrade the DAO enzyme, plus they can also produce histamine themselves, so it’s a double whammy
  • Gluten intolerance
  • Leaky gut
  • DAO-blocking drinks: alcohol, energy drinks, tea
  • Genetic mutations (common in people of Asian descent)
  • Inflammation from Crohn’s, ulcerative colitis, and inflammatory bowel disease
  • Medications:
    • Non-steroidal anti-inflammatory drugs (ibuprofen, aspirin)
    • Antidepressants
    • Immune modulators
    • Antihistamines
    • Histamine (H2) blockers

Histamine-rich foods:

  • Aged cheeses, including goat’s cheese
  • Cured meats: bacon, salami, pepperoni, luncheon meats, hot dogs
  • Dried fruit: apricots, prunes, dates, figs, raisins
  • Fermented alcoholic beverages, especially wine, champagne and beer
  • Fermented foods: sauerkraut, vinegar, soy sauce, kefir, yogurt, kombucha, etc
  • Most citrus fruits
  • Nuts: walnuts, cashews, peanuts
  • Soured foods: sour cream, sour milk, buttermilk, soured bread, etc
  • Smoked fish and certain species of fish including mackerel, mahi-mahi, tuna, anchovies, sardines
  • Vegetables: avocados, aubergines, spinach, and tomatoes
  • Vinegar-containing foods: pickles, mayonnaise, olives
  • Leftovers – the longer they have been kept, the more histamine they will contain

Histamine-releasing foods:

  • Alcohol
  • Artificial preservatives and dyes
  • Bananas
  • Chocolate
  • Cow’s milk
  • Nuts
  • Papaya
  • Pineapple
  • Shellfish
  • Strawberries
  • Tomatoes
  • Wheat germ

Low-histamine containing foods:

  • Cooked eggs
  • Cooking oils: olive oil, coconut oil
  • Dairy substitutes: coconut milk, rice milk*, hemp milk, almond milk
  • Fresh fruits: mango, pear, watermelon, apple, kiwi, cantaloupe, grapes
  • Fresh vegetables (except tomatoes, spinach, and aubergines)
  • Freshly caught fish
  • Freshly cooked meat or poultry
  • Gluten-free grains*: rice, quinoa, corn, millet, amaranth, teff
  • Herbal teas
  • Leafy herbs

How do you deal with a histamine intolerance?

Firstly, you can try and reduce the symptoms via diet (excluding the high histamine and histamine-releasing foods) and taking certain supplements such DAO.  I know some people have had issues sourcing DAO supplements in the UKIf this is you, contact the Tummy Team on and we will help you source them.

The main thing though is to figure out the root cause as to why you have this build-up of histamine in your body. In my experience, it is usually down to poor gut health and an overgrowth of bacteria that can release histamine and degrade DAO, such as is the case in SIBO.

* If, after a SIBO test, you find that the root cause of your histamine intolerance is SIBO, then you may have to avoid certain gluten-free grains for a short period of time, this includes rice milk.  

For more information about SIBO, read my SIBO blog here.