Sometimes it seems that with Irritable Bowel Syndrome, there are more questions to be asked than we have answers for. It truly is a complex condition that researchers are still trying to fully understand. For instance, what causes IBS? It’s likely due to a combination of factors, and not one isolated cause. Maybe you’ve heard stress is to blame, or food poisoning, or genetics? How about histamine intolerance?

Today’s guest post is coming to us from Registered Dietitian Wendy Busse. Wendy is an expert on histamine intolerance, and today she’s going to explain to us what histamine intolerance is and how it might be related to IBS. Be sure to check out Wendy’s bio below if you’re interested in learning more from Wendy about this fascinating topic!

The first step if you’re looking to improve irritable bowel syndrome (IBS) or another digestive disorder or disease, is to understand more about the Low FODMAP diet and if it can help. Download my free eBook to help you better understand this diet and get started implementing simple steps to get rid of symptoms like gas, bloating, pain, diarrhea or constipation related to IBS. Click here to get a copy emailed to you right away.

What is Histamine?

Histamine is an inflammatory compound that helps our immune system fight infections. It is also released during allergic reactions.

In addition to being a naturally occurring compound in our bodies, histamine can also be found in the foods we eat. A quick search online will leave you lots of information on which foods contain histamine, but unfortunately, much of this information is inaccurate. There has not been much research on this topic and there is still a lot that we need to learn. Many foods that are commonly listed as being high in histamine have never actually been tested for histamine, so proceed with caution with the information you find online! With systematic experimentation, you can find helpful dietary and lifestyle changes.

Histamine intolerance is not generally well accepted by the medical community in Canada and the United States, but it is much more recognized in Europe. This is likely because most of the current research being done on histamine intolerance is coming out of Germany and Austria.

What Causes Histamine Intolerance?

In healthy bodies, histamine from food is broken down by an enzyme known as diamine oxidase which is found in our digestive system. If the activity of this enzyme is reduced, our ability to break down histamine is compromised, resulting in the histamine being absorbed into the body. In people with histamine intolerance, diet may contribute to high blood histamine levels.

Possible causes of decreased activity of diamine oxidase include:

  • Genetically decreased production of diamine oxidase
  • Certain medications
  • Foods that are high in compounds similar to histamine
  • Inflammation in the digestive system



Symptoms of Histamine Intolerance

People with a histamine intolerance usually exhibit symptoms that overlap with IBS. Diarrhea, constipation, abdominal pain, and burping are common. A key difference between histamine intolerance and IBS is that histamine intolerance causes multi-organ symptoms. If you have digestive symptoms only, you probably don’t have histamine intolerance.  Common symptoms of histamine intolerance include:

  • Skin: itching, flushing, hives, swelling
  • Respiratory: red itchy eyes, sinus pain, nasal congestion
  • Digestive: diarrhea, constipation, abdominal pain, burping
  • Other: headache

It is important to keep in mind that the symptoms described above can have many causes. Just because you have these symptoms does not mean that you have histamine intolerance and need to follow a low histamine diet and/or take diamine oxidase supplements. These changes are only needed if they are truly helpful.

Diagnosing Histamine Intolerance

Histamine intolerance should be suspected if you have some of the common symptoms (listed above), especially if the symptoms are affected by dietary changes. Another red flag for histamine intolerance would be symptom relief with antihistamine medication. This includes medications for typical allergy symptoms (Benadryl, Claritin, Aerius, etc.) and digestive symptoms (Zantac, Tagamet, Pepcid, etc.). Unfortunately, there are no universally accepted laboratory tests to diagnose histamine intolerance. Therefore, the diagnosis is based on symptom improvement with treatment.


Histamine Intolerance and IBS

When histamine isn’t broken down and is absorbed into the body, it can lead to a variety of troubling symptoms. It is even thought that histamine intolerance could be to blame for Irritable Bowel Syndrome in some cases. Recent research is starting to shed some light on this relationship. There is not enough information to make definite conclusions, but it may be the start of a theory on how histamine intolerance and Irritable Bowel Syndrome overlap.

One study found that people with low diamine oxidase enzyme blood levels were more likely to have carbohydrate malabsorption (measured by lactose and fructose breath hydrogen test). A different study found reduced histamine in the urine after subjects with IBS followed a low FODMAP diet. Although the association between FODMAPs and histamine levels is weak given the current research, it will be interesting to see what further research turns up in the future.



Histamine Intolerance and SIBO

It has also been observed that small intestinal bacteria overgrowth (SIBO) may lead to histamine intolerance, as clients with SIBO commonly report histamine intolerance symptoms. Since histamine is formed when bacteria in the gut break down the amino acid histidine, it makes sense that an overgrowth or imbalance of gut bacteria could impact the production of histamine in the body.


Gut Bacteria and Protein Digestion

Amino acids are the building blocks of the proteins in the foods we eat. If protein was a pearl necklace, each pearl would be an amino acid. In the digestive system, protein is broken down into amino acids, which are then absorbed into the body. In healthy bodies, there are very few bacteria in the part of the digestive system where the protein digestion and amino acid absorption takes place. However, if there is an overgrowth of bacteria, some histidine may be converted to histamine.

How to Treat Histamine Intolerance

Histamine intolerance can be improved with a combination of a low histamine diet, diamine oxidase supplements, and antihistamine medications. Much like managing IBS successfully, it takes systematic experimentation to find the most beneficial treatments for histamine intolerance. Working with a knowledgeable and caring health care professional (such as a Registered Dietitian), can make this process much easier.

Low Histamine Diet

A low histamine diet limits foods that are high in histamine and foods that may potentially cause a release of histamine in the digestive system. High histamine foods are very individual, so unfortunately there isn’t a one-size-fits-all list of foods to include and avoid.

Bacterial growth in food, such as fermented foods and leftovers, are susceptible to high histamine levels. Additionally, certain fruits and vegetables such as spinach and tomatoes are thought to be high in histamine, especially when overripe. Other foods such as egg white are considered to be histamine-releasing foods. This concept is very popular, even in medical journal articles, but we lack solid evidence to suggest that any food can cause a direct release of histamine in the digestive system.

A low histamine diet helps some people feel better, with symptoms usually improving within one week. If a low histamine diet has not made a noticeable difference within four weeks, the diet should be discontinued.

Diamine Oxidase Supplements

As described above, low diamine oxidase enzyme activity may lead to reduced histamine breakdown and increased absorption of histamine into the body. Luckily, the diamine oxidase enzyme is available as a supplement. The supplement is taken prior to meals and works by breaking histamine down in that meal, with potential benefits assessed very quickly.


Wendy Busse is a Registered Dietitian with a passion for helping clients that suffer from unexplained food allergy symptoms. Wendy strives to provide information, resources and support to helps clients improve their symptoms through dietary changes without over-restricting. Wendy lives in Canada with her husband, two teenage daughters and cat. Her hobbies include cooking, yoga, cross country skiing, photography and hamlaxing (which is a word her family made up for relaxing in the hammock).




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