Histamine Intolerance - what do we know so far?

Let’s start with the basics. What IS histamine?  

Histamine is a chemical messenger, which has several important roles in our body. These include the release of stomach acid and muscle contraction. 

Histamine usually doesn’t cause any issues because its tightly regulated.  

So, what is histamine intolerance?    

Histamine intolerance is when histamine levels in the body rise, resulting in uncomfortable symptoms. This happens when the body is unable to regulate the amount of histamine within normal levels. So why does this happen?   

Well, there are two main causes of histamine intolerance:   

1. Over production of internal histamine. This can happen due to conditions like Mast Cell Activation Syndrome (MCAS), mastocytosis, allergies or an imbalance in gut bacteria.  

2. Reduction of histamine breakdown. This can be a result of some medications, genetics, hormones and gut diseases like inflammatory bowel disease. 

Sometimes people experience both! So, it's possible to overproduce histamine AND have a problem with histamine breakdown.   

What are the symptoms of histamine intolerance?   

Histamine intolerance can affect every single system in our body. This means that symptoms are wide ranging, and include the following:    

• Gut symptoms like bloating, constipation, diarrhoea, abdominal pain and cramps, nausea and vomiting.   
• Respiratory symptoms such as nasal congestion, rhinitis, shortness of breath.   
• Skin symptoms such as rashes, flushing and swelling.   
• Nervous system symptoms such as headaches, dizziness and fatigue.   
• Cardiovascular symptoms such as increased heart rate and sudden drops in blood pressure.   
• Reproductive symptoms like painful periods. 

You may only have a few of these symptoms, and you definitely don’t need to have them all to have histamine intolerance. Symptoms often change day to day and can, also, change as we age.  

How is histamine intolerance diagnosed?   

Currently there is no single test that can diagnose the condition. This can make diagnosis tricky as the symptoms can often be quite generalised.

However, histamine intolerance should be considered if you have more than two of the symptoms listed above.  These symptoms could be caused by many other conditions, so it is important to work with a Health Professional that can rule these out first.   

If histamine intolerance is suspected, the next step is to trial a low histamine diet for 2-4 weeks to see if there are any improvements.  If there is an improvement, this suggests histamine intolerance. From here you re-introduce foods one by one. This helps identify personal sensitivities and how much histamine you can cope with in your diet before you develop symptoms.   

A low histamine trial should only eve be done with the support of a Dietitian experienced in histamine intolerance. This is because the diet can be socially and nutritionally restrictive, which can be stressful. This is a problem as stress itself can increase histamine production! 

How is histamine intolerance treated?   

There are a couple of options for treating histamine intolerance:  

1. A low histamine diet. The main treatment is reducing your dietary intake of histamine in food and drink. It's impossible to avoid histamine completely so the goal is to work out how much you can tolerate. Keel in mind that a person's ability to tolerate histamine in foods may fluctuate depending on other factors (see below)  
2. Diamine Oxidase (DAO) supplements These can be used alongside the diet, if you have issues breaking down histamine. DAO is an enzyme found in the body that breaks down histamine in the food that we eat. There are a few small human studies that show some benefit of supplementing these enzymes in people with histamine intolerance. These studies used DAO made from pig kidney extract. If you're plant-based, DAO made from legumes is available, but we have no human studies yet so we can’t say how well they work. 
3. Antihistamines can be used when severe symptoms remain even when using the above strategies. Current guidance suggests their use should be short term though.  

What foods contain histamine?   

Good question! If you've ever looked online for a guide to which foods contain histamine, you’ll know that there are HUNDREDS of lists, and they all differ!  

The problem is that we don’t yet have a ‘gold standard’ list. This is in part because storage, transport and processing of foods can all affect histamine levels. So, a piece of salmon you eat at home today may have different levels of histamine to a piece of salmon you eat in a restaurant next week!   

Foods high in histamine include:  

• fermented foods 
• aged and processed meats 
• some fish such a tuna and salmon 
• some plant-based foods such as tomatoes.  

But, there is PLENTY of food you can eat when reducing histamine intake.   

Is there anything else apart from food that increases histamine levels?   

Absolutely! How you tolerate histamine may vary at different times due to external factors impacting histamine levels in body. Other factors that can increase histamine levels include:   

• Stress  
• Illness  
• The menstrual cycle   
• Response to allergens e.g. hay fever    

Is there any link between hormones and histamine?   

Yes. Increasing levels of oestrogen can increase how much histamine your body produces. In turn histamine can increase oestrogen production resulting in a vicious cycle! 

Because oestrogen levels fluctuate throughout the menstrual cycle, women with histamine intolerance may experience more symptoms during the second half of their menstrual cycle.  

Is there any link between the perimenopause and histamine intolerance?   

Quite possibly! Research is scarce, but we are seeing many women with symptoms of histamine intolerance during the menopause in clinical practice.  

During peri-menopause oestrogen can peak at higher levels than in a normal menstrual cycle. This may explain why we are seeing women presenting with histamine intolerance during this time.   

So, where do we go from here?....  

Most of the research we have about histamine intolerance has been published in the last 10 years and we're learning more about the condition all the time. Although there are still questions to be answered, this isn’t a condition you should self-diagnose or manage on your own. Management can be challenging and information online is not always accurate.  Here are some key things to remember:

1. Histamine intolerance can affect your whole body and the symptoms can vary   
2. The main route to diagnosis is assessment of symptoms and then trialling a low histamine diet for 2-4 weeks.   
3. It’s important to get support if attempting the low histamine diet.   
4. There are other things to consider when controlling histamine levels, not just food. 

If you think you might have histamine intolerance, the first step could be to keep a food and symptom diary to see if there is a pattern between high histamine foods and your symptoms. This can then be discussed with a Health Professional with experience in this area.

How to learn more

You can reach out to Chloe through her website. She has also developed a short course on the low histamine diet which you can learn more about here.

At Field Doctor, we are always looking for new ways to support your health and make managing health conditions easier. We are currently looking at the feasibility of developing some low histamine meals. If this is something that would benefit you, we’d love to hear from you—please register your interest here.

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