What is Histamine Intolerance? The Ultimate Guide
Could you be histamine intolerant?
If you've been itching and scratching in response to food, developing hives and anxiety and even digestive issues to boot - you may have histamine intolerance.
What’s histamine intolerance? Well, it’s a very under-recognized - but very real - disorder that may be behind all of your strange, allergy-like symptoms.
Today, I’ll give you the lowdown on everything you need to know about histamine intolerance.
What is histamine intolerance?
Unlike a typical food sensitivity, histamine intolerance is not a simple sensitivity to the compound histamine. It’s a problem that develops when your body is unable to cope with the amount of histamine in your system - therefore causing body-wide reactions.
To understand how and why histamine can cause a problem, let’s begin to explore the reasons behind this intolerance by answering a few questions…
What is histamine?
While histamine is a chemical messenger compound that communicates with the brain, it is also involved in processes like stomach acid secretion, which is involved in digestion. The main action of histamine, however, that we’re interested in today, is its role in immunity.
Histamine is a compound the body makes as part of the defence pathway when the local immune system is triggered. The compound acts as the mediator of any substance the body views as a threat, and it is held in little capsules, called mast cells and basophils1.
Mast cells are located in high concentrations in the skin, lungs, nose, mouth, digestive tract and the bloodstream2, while basophils are brought to the site once the immune response has been triggered3.
What causes the body to release histamine?
There are a number of reasons for histamine release to occur, but it is typically as a result of the immune system feeling unsafe, or under threat. When you’re stung by a bee, for example, histamine jumps into action to immediately bring help to the site to control the venom. Swelling, itching and redness occur as a result. Sometimes, even if the substance that comes into contact with the body is not necessarily harmful, the body may still perceive it as such, and histamine goes to work.
Outside of foreign invaders, substances such as pollen, dust, pet dander, chemicals, and even foods in your daily diet can trigger the release of histamine4.
What does histamine do?
When released by the mast cells, histamine triggers other systems of the body to jump into action. Throughout the body, there are locations on specific cells, called receptors, which allow histamine to bind in a lock-and-key fashion. Once histamine locks into these receptors, it switches on a response. The four known histamine receptors are denoted H1 - H4 and, depending on their location, a specific response is elicited5.
H1: They are expressed on the cells that line certain organs like the nose, mouth and digestive system. They are also located within the muscle tissue of the lungs, which is a major source of triggers of allergic reaction6. Within the brain and spinal cord, H1 receptor activation triggers behavioural effects.
H2: Located within the stomach, these receptors turn on the process of the stomach to release acid7.
H3: Within the brain and spinal cord, H3 receptor activation plays a role in behavioural effects as well as body temperature changes8.
H4: The most recently discovered histamine receptor is one involved in the regulation of all other immune system cells, and plays a role in activating or inhibiting their functions9,10.
For example, a reaction causes the heart to beat faster to ensure that blood can pump through the body at an increased pace, to bring other nutrients and working cells to the site of ‘infection’ more quickly.
The more histamine is released, the more these receptors are activated, the higher the response will be felt throughout the body. When histamine release is chronically triggered, it leaves you with a multitude of undesirable symptoms.
Chronic histamine release and/or a reduced capacity of the body to manage it and get rid of the compound results in internal histamine levels being too high and causing such reactions - this is the condition we know as histamine intolerance11.
Problem with high histamine levels
When the triggering events continue, the body will continue to release histamine, which is why you will end up having to deal with some of the common symptoms of histamine intolerance.
These symptoms are typically widespread throughout the body and, thinking back to where the histamine receptors are located throughout the body, explains why a reaction can affect every system in your body and cause it to dysfunction.
So, what is it that causes high histamine levels, and how can you help the body to manage histamine levels like it should?
4 main factors that cause high histamine levels
There are several causes of histamine intolerance. Below are four of the main ones that could be impacting your body.
1. Enzyme insufficiency
Your body has two primary ways of breaking down histamine. Both involve enzymes, where one is called diamine oxidase (DAO for short) and the other, histamine N-methyltransferase (HNMT). If these enzymes are in short supply, histamine levels rise and are not appropriately lowered back down to normal level.
DAO is a more widespread means of histamine breakdown, whereas HNMT break down histamine within cells13.
DAO can either be made in short supply, or it can be used up in other processes, leaving too little available for the breakdown of histamine. Certain medications like non-steroidal anti-inflammatory drugs (NSAIDs) may also block the release of DAO, while simultaneously increasing the release of histamine. As do certain foods, which you will learn more about in the sections below.
2. Bacterial overgrowth
Because some of the bacteria that live in your gut release histamine, too many of these certain types can elevate the levels of histamine your body had to deal with. Fungus that can overgrow in the gut - like candida, for example - promotes histamine release as a means for the body to try to kill the excess.
And, believe it or not, even ‘good’ bacteria convert the amino acid histidine into histamine - a usually harmless process. The bacterial contributions are really important, because this means that taking probiotics can actually make histamine symptoms worse!
Ensure you’re taking a low histamine probiotic that contains only low histamine bacteria. You can find a list of low histamine probiotics which are safe for histamine intolerance, as well as high histamine probiotics to stop taking immediately here.
3. Mast cells
Histamine is typically released from mast cells in response to allergens, however if mast cells are unstable or become overactive, histamine can be released at higher-than-normal levels.
Mast cell destabilization and malfunction can occur for many reasons, such as an H. pylori infection or other biological or inherited dysfunctions.
Most histamine intolerance sufferers will experience mast cell issues to at least some degree, and it’s why the most common and effective therapy I use is a particularly potent mast cell stabilizer, which has allowed the majority of my clients to eat more foods with less symptoms, in as little as 10 days. You can find my recommendation for the top histamine supplement here.
4. Digestive disorders
The term leaky gut is commonly used to describe the cause of a range of different health issues. But what is it?
Well, normally, the digestive tract is selectively permeable, meaning it allows certain nutrients to pass through the gut and enter the body - while also filtering out potential threats such as toxic compounds, pathogens and whole food particles.
This mechanism allows us to let the good stuff in, while keeping the bad stuff out - make sense?
When leaky gut has developed, on the other hand… the digestive tract has become even more permeable, meaning larger molecules are allowed to move into the bloodstream, which would normally be filtered out and eliminated from the body.
When these larger molecules enter the bloodstream, the body does not recognize them and therefore reacts with an immune response, involving inflammation and histamine release.
Not only does this scenario place more demand on the DAO enzyme to reduce histamine levels, but inflammation in the gut decreases DAOs ability to perform and further contributes to the problem.
As a result of any of the above, you’ll begin to experience the symptoms of high histamine levels.
Symptoms of histamine intolerance
High histamine levels result in a variety of symptoms, often corresponding to the receptors which histamine normally binds to and activates. We can, therefore, categorize the symptoms into the areas of the body where these histamine receptors are found:
Nervous system symptoms:
The most common symptom of histamine intolerance that affects the nervous system is headaches. Migraines are a common manifestation of high histamine levels14.
In fact, recent research proposes that headaches or migraines arising from the consumption of alcohol may be more likely to develop due to histamine reactions rather than from the alcohol itself14.
Lung and respiratory tract symptoms:
Respiratory manifestations as a result of high histamine levels include runny nose, wheezing, difficulty breathing, coughing and asthma-like symptoms15.
Atopic dermatitis and chronic urticaria are associated with histamine intolerance, as are flushing, swelling, itching and increased warmth in the skin upon acute increase in the body’s histamine levels16.
Reproductive system symptoms:
Women who have histamine intolerance may have associated irregularities in their menstrual cycle and suffer more frequent headaches during this time due to the link between histamine and female sex hormones that correlate with reproduction17.
The digestive tract not only has a high concentration of histamine receptors, the bacteria that live in your gut also produce histamine during their role in food breakdown and, when you add the foods you consume that are higher in histamine, there’s little wonder why histamine intolerance results in such severe digestive disturbances like cramps, diarrhea, flatulence and bloating18.
High histamine levels have also been implicated in a number of digestive diseases like Crohn’s, ulcerative colitis, food allergies and even colorectal cancer19.
It is the role of histamine in the early response of inflammation that causes these symptoms, which may be either acute/short-acting, or chronic/long-standing20.
I’ve created a blog post which contains a more comprehensive list of histamine intolerance symptoms.
Now, you may be looking at the symptoms in the body systems above and asking the question: how do you know if you have histamine intolerance?
To obtain an answer, think about when your symptoms are most severe.
Do you get a runny nose and itchy eyes after you eat tomatoes, avocados or drink tea?
Do you have a diagnosed food allergy or intolerance?
And do you often suffer from sinusitis, asthma-like symptoms or experience flushing of the face and neck when you drink even small amounts of alcohol?
Any of these can indicate that your body is just not coping with its histamine levels, and you need to do something about it to find relief.
Fortunately, there are a few ways you can help your body out. And, one of the quickest ways to improve symptoms and confirm your histamine intolerance is to address your diet...
Which foods are high in histamine?
To start giving your body the break it needs, you need to look at the foods that are high in histamine, so that you may begin to reduce them in the diet.
How does diet play a role? Well, because of how histamine activation works in the gut.
The foods on the following list influence histamine in a number of ways. They can either...
- Increase the amount of histamine released into the body (these are histamine-releasing foods)
- Block that enzyme we mentioned earlier, called DAO - the one that is responsible for degrading histamine - (these are DAO-blocking foods)
- Or, they are simply higher in histamine levels, which increases the amount the body has to deal with (high histamine foods)
By controlling histamine levels with your diet, you can control how much external histamine you’re putting into your body, and in doing so, reduce the load your body has to deal with21,22.
Below is a general list of foods and medications that impact histamine intolerance. This list is not fully comprehensive - however, I've created a post with the comprehensive list of high and low hismine foods.
For a quick overview, let’s start with the foods that are high in histamine, that you need to stay away from as much as you can, first:
- Black and green tea
- Green bell peppers
- Legumes – green peas, red beans
- Processed meat (salami, sausage, etc)
- Vinegar and pickled items (apple cider vinegar is high in histamines, too)
- Raw egg
- Cheese - fermented
- Soy and soy products
- Kefir and yoghurt
- Citrus fruit (this includes oranges, lemons and limes)
- Berries – depending on ripeness – check symptoms
- Cheese – processed
- Dried fruit
- Walnuts and cashews
- Over-ripe vegetables
- Any leftover food not stored in the fridge immediately after cooking
- Commercial salad dressings with vinegar
- Chocolate and cocoa
- Fermented cabbage
- Yeast containing breads and cakes
- Sour cream
- Pineapple (not the bromelain extract, however! This pineapple extract canactually act as a naturalantihistamine)
- Olives (not their oils)
But WAIT! Before you shout out in protest and demand to know what you can eat… believe it or not, the list is actually longer. Here’s a list of low-histamine foods to enjoy:
- Sweet potato
- Red lettuce
- Rice (brown/wild)
- Fresh corn
- Red apple
- Beetroot (fresh)
- Chinese cabbage
- Egg (completely cooked)
- Butternut squash
- Milk substitutes (rice, hemp, almond)
- Leafy herbs like basil, thyme, rosemary, sage, oregano, peppermint
- Gluten-free wholegrains like quinoa, millet, sorghum, buckwheat
- Fresh beans and lentils (not red)
- Coconut milk
- Red onions
- Raw honey
- Chia seeds
- Hemp seeds
- Sesame, sunflower, pumpkin (pepita) seeds
- Red cabbage
- Olive and coconut oil
- Pure peanut butter – no other ingredients
- Flaxseed meal
- Freshly caught fish
- Freshly cooked meat and poultry
- Any other vegetable not mentioned on the foods to reduce list
- Herbal tea
By controlling histamine levels with your diet, you can control how much external histamine you’re putting into your body, and in doing so, reduce the load your body has to deal with.
On top of foods, there are also drugs or medications that may increase histamine release, promote it’s liberation, or block the DAO enzyme. These include some specific types of24:
- Muscle relaxants
- Pain relievers
- Blood pressure medication
- H2 receptor blockers
If you are on one of these classes of medication, speak to your doctor about your alternative options when it comes to their histamine influence.
If you manage the external factors like food and medication, it provides a simple and immediately effective method on how to reduce histamine release from your body.
To access the free, comprehensive Low Histamine Food List and get all of the tips and tricks for starting your new diet, click the button below.
How is histamine intolerance treated?
Now that you know what histamine intolerance is, how you develop it and the diet you can follow to reduce its effects, let’s get into how histamine intolerance is treated.
Unfortunately, histamine intolerance is one of those difficult to diagnose conditions as the symptoms are so vast, and they affect many different organ systems.
Individuals may have a range of different symptoms and so a diagnosis is typically based on a thorough history taking, and a look into the trigger of the symptoms. One of the best ways the body will indicate that there’s an issue with histamine load is through the development of symptoms25 after eating or drinking high histamine foods. The best way to do achieve a diagnosis is through the help of a healthcare professional, such as a doctor knowledgeable in functional or integrative medicine, a naturopath, or a qualified nutritional therapist.
Should these professionals not be an option for you to approach right now, there’s a process you can follow yourself to determine if histamine may be a problem for you:
Start taking note of the symptoms mentioned above when these foods are still in your diet. Continue to monitor your symptoms for 5 days to a week.
Now, for the next 10-14 days, dramatically reduce your intake of high histamine foods on the ‘avoid’ list, and only consume ‘allowed’ foods according to this low histamine diet food list. Continue to take note of your symptoms during this time.
It’s important to be quite strict in this phase in order to make the most of your body’s ability to reduce the current histamine load.
Lastly, reintroduce one or two of the higher histamine foods at a time, and take note of your symptoms. This phase may last up to 6 weeks. Also take note as to whether there are external influencing factors at play, like stress, the use of medication, or menstruation, for example26.
If you develop symptoms in response to the high histamine food reintroduction, this is a strong indication that histamine is not being effectively broken down by your body. And, it’s time to start a histamine intolerance protocol, to help you to determine why, and what your next steps can be to start your journey to health and wellbeing.
For a more comprehensive at-home test for histamine intolerance, as well as a method for food reintroduction, check out this post on a DIY at-home test for histamine intolerance.
Can histamine levels be clinically tested?Although tests for histamine intolerance have been proposed in various scientific studies, the majority have limited availability or are not available for public use.
Most reliable tests for histamine intolerance must be obtained through a specialized practitioner. Below is a breakdown of clinical methods for testing histamine intolerance:
1. Determining DAO activity in the blood or in the intestines
It may be valuable to determine how much DAO is active in the blood, however, there is evidence to suggest that this does not provide a conclusive result as DAO is active in a number of tissues when it is needed, instead of remaining in the bloodstream27.
In the intestines, measurement of DAO activity may provide significant evidence as to whether there is a histamine issue; there is a need for more scientific evidence to be conducted regarding this testing method.
2. Histamine 50-skin-prick testWhile not available for public use, there has been development of a test that determines how quickly histamine is able to degrade in 50 minutes28.
As this test measures how quickly your body breaks down histamine, it provides a great method for understanding if normal levels of histamine may cause a reaction due to a slower-than-normal degradation rate.
3. Stool tests for histamine intolerance
Because bacteria also produce histamine, it has been proposed that a stool analysis may give an indication as to what is going on with an individual’s histamine levels29.
The very fact that these bacteria do produce histamine, raises questions as to whether the amount of histamine in a stool sample is due to an increase in metabolism of it by the bacteria, or whether there is an intolerance or toxicity29.
Treating histamine intolerance
Mainstream medical treatment approaches to histamine intolerance symptoms typically involve the use of antihistamine pharmaceutical drugs, or, in severe cases, steroids, which suppress the immune system.
The most widely available antihistamines block H1 receptors, while there are also those available that target the H2 receptors in the gut. It has, however, been noted in a review study, that these drugs only control the symptoms related to the histamine response, and not the underlying cause of the disorder30.
These drugs have also been proposed to work in an acute setting of histamine toxicity, which means they are not supposed to be taken long-term31. If you’re looking to find out how to break down histamine naturally, outside of the changes you can already start making to your diet, we can begin to explore supplementation.
How to lower histamine naturally with supplements
One of the areas of current research in histamine intolerance therapies involves the function, or rather dysfunction, of the DAO enzyme.
There have been implications that one of the most common causes of low DAO is genetics, which has resulted in an increase in the risk of histamine intolerance, or increased histamine sensitivity.
While there is plenty of evidence to support the fact that a low-histamine diet can reduce histamine levels within the body, a low histamine diet also improves DAO levels at the same time, allowing the body to really begin coping with the demand32.
In addition to diet, another way to increase the activity of DAO is to increase the intake of the nutrients DAO needs to be produced and function.
Fatty acids. We already know the importance of fatty acids, like omega 3s, on our overall health. Now, we can add histamine intolerance to that list. A recent study has shown that long chain fatty acids, especially those of saturated and monounsaturated variety, improve DAO activity. Olive oil, coconut milk, and coconut oil are good examples.
Low levels of copper, zinc and magnesium have also been implicated in reduced DAO activity. While there was no particular correlation between the increase in DAO and the intake of supplemental copper in experiments, DAO activity has been shown to increase with the addition of magnesium and zinc supplements33.
- DAO supplementation. In some cases, especially where genetics is the cause of low DAO production, a supplemental form of the enzyme may be necessary. In studies, it has been shown to be effective in the treatment of histamine related symptoms, in particular, episodes of headache or migraine, in those with histamine intolerance 34,35.
- Mast cell stabilizers. Histamine is released from mast cells within the body and, when histamine levels are too high, stabilizing mast cells can be a huge help for reducing the amount of histamine being released. The use of mast cell stabilizers therefore reduces the overall histamine levels in the body and calms symptoms. Natural mast cell stabilizers can act just like antihistamines in their ability to calm symptoms. The strongest natural mast cell stabilizer that I recommend nearly all of my clients can be found here.
With more information and activity surrounding histamine intolerance in the media and online, scientists have started to pay attention.
More studies are being conducted into the problem, and with it, comes more solutions. This change brings with it a significant amount of hope for all of us for the future of our condition.
Finally, having some form of evidence for an issue we have struggled through with daily chronic symptoms, having been told there’s nothing wrong, or that it’s just allergies.
With this Ultimate Guide to Histamine Intolerance in your toolkit, you can begin your plan of attack on histamine intolerance. Start making the changes to your diet and supplement routine right now, to not only decrease your histamine levels, but to enable your body to begin managing its histamine load on its own.
Now you can fight histamine intolerance and its long list of dreadful, debilitating symptoms… and win!
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