In recent studies, Pseudomonas aeruginosa has emerged as a notable histamine-producing bacterium within the gut microbiome, shedding light on its potential role in digestive health and histamine-related disorders. These tiny bacteria can have big impacts on our health, especially when they start to overgrow within our gut microbiome. When the delicate balance of our microbiome is disrupted (gut dysbiosis), that’s where Pseudomonas aeruginosa and histamine intolerance come to a crossroads.

In today’s article, I’ll introduce you to the understanding we now have about the connection between gut bacteria and histamine intolerance and why and overgrowth of Pseudomonas aeruginosa is so problematic for people with Histamine intolerance, MCAS, and CIRS. I’ll also discuss how to test for the presence of Pseudomonas in your gut.

If you have high levels of Pseudomonas aeruginosa, this may be one of the reasons behind chronic symptoms such as headaches, migraines, nasal congestion, fatigue, digestive problems, skin reactions (such as hives or flushing), anxiety or palpitations, asthma, allergies, chronic bronchitis, cystic fibrosis, and other lung diseases. (*). Finally, I’ll explain how Functional Medicine addresses Pseudomonas aeruginosa and histamine intolerance.

Pseudomonas aeruginosa: What Is It?

Pseudomonas aeruginosa is a gram-negative bacterium often found in the human gastrointestinal (GI) tract in patients who have histamine intolerance. Considered an opportunistic pathogen, it can cause GI tract infections, diarrhea, colitis, fever, headaches, and many of the classic symptoms associated with Histamine intolerance, CIRS, and MCAS. This occurs because Pseudomonas aeruginosa is a histamine-producing gut bacterium (*).

The link between gut bacteria and histamine intolerance is not a new concept, but it is gaining attention in the field of Functional gastroenterology.

If you have gut dysbiosis, and specifically an overgrowth of histamine-producing bacteria, when these bacteria multiply, the histamine they produce can contribute to your histamine bucket.  The balance between histamine-producing gut bacteria and histamine-degrading bacteria is an important area for functional medicine practitioners who work with patients who have inflammatory histamine-driven conditions.. 

How Pseudomonas aeruginosa Produces Histamine

Pseudomonas aeruginosa converts certain amino acids, like histidine, into histamine through enzymatic reactions. Histidine decarboxylase (HDC) is an enzyme that catalyzes the conversion of the amino acid histidine into histamine, which is a biogenic amine. Histidine decarboxylase is found in various tissues, including the brain, stomach, and immune cells, where it participates in histamine production. This enzyme is crucial for maintaining histamine levels in the body, which in turn are important for processes such as inflammation, gastric acid production, and neurotransmission.

When you have an overgrowth of these opportunistic bacteria and too much of this histadine to histamine conversion, you could potentially have excess histamine.  Recently, Pseudomonas aeruginosa has been shown to also stimulate neutrophils to release histamine, which is a bit unusual. Typicaly, when we think about histamine, we think about Mast cells and Eosinophils.  But this research shows that most types of white blood cells are capable of producing histamine.

Gut Bacteria And Histamine Intolerance

As I mentioned earlier, there is an important connection between our gut bacteria and histamine. Certain bacteria within our gut microbiota can be categorized as histamine producers or histamine degraders (histamine degraders break down excess histamine within the gut). Histamine-producing gut bacteria produce histamine by converting the amino acid histidine into histamine through an enzymatic reaction. For the nerds out there (like me), this process involves the enzyme histidine decarboxylase (HCD), which certain bacteria possess.

Certain species of gut bacteria, such as some strains of Lactobacillus, Enterobacteriaceae, Morganella morganii, H.pylori, and other genera, can produce histidine decarboxylase. Some of these bacteria can be part of the normal gut flora, while others are considered opportunistic or even pathogenic. In other words, even good bacteria produce histamine. Remember, histamine is needed in the body, and it’s only a problem if we have too much of it or we can’t metabolize or “degrade” it.

Today, I want to share with you another type of gut bacteria known to produce histamine: Pseudomonas aeruginosa. The presence of Pseudomonas aeruginosa in the gut, even at low levels, can influence immune responses.

At low levels, this bacterium has been shown to cause gut inflammation, exacerbating conditions like inflammatory bowel disease. Pseudomonas aeruginosa has also been shown to drive airway inflammation and constriction (*). This may be of interest to you when discussing asthma, COPD, and other breathing issues. This also highlights that our gut bacteria can affect our lungs. This is a new area of interest as it relates to something called the gut-lung axis (*).

More recent studies have suggested that bacterial histamine release in the gut does not only cause problems in the gut, but can also have immunological consequences at distant mucosal sites, such as in the lungs, sinuses, and urogenital tract (*)  

The gut-lung axis plays a significant role in influencing lung health, impacting various respiratory conditions and diseases. It is linked to respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), where interactions between the gut and lung microbiomes can affect the onset and progression of these illnesses (*),(*).

Furthermore, the gut-lung axis is associated with lung cancer(*), with some studies suggesting a potential role of gut fungi in the disease’s development. Additionally, viral respiratory infections like respiratory syncytial virus (RSV) can be influenced by gut microbiota.

What Causes Pseudomonas aeruginosa Overgrowth

The growth and presence of Pseudomonas aeruginosa in the gut can be influenced by various factors, including antibiotic use, diet, and overall health of the host. Imbalances created by antibiotic treatments, for example, can sometimes favor the growth of resistant bacteria like Pseudomonas aeruginosa.

Remember a poorly balanced gut microbiome can cause an increase in histamine producing bacteria and a decrease in histamine-degrading bacteria, This is why if you or someone you love is suffering with histamine intolerance or MCAS, evaluating and having a better understanding of the gut microbiome can make all the difference in treatment outcome.

You can read more about what kinds of bacteria are histamine producing here

Pseudomonas aeruginosa and Histamine Intolerance

Histamine intolerance originates in gut, multiple studies have now confirmed this (*). Pseudomonas, being a histamine-producing gut bacteria reiterates the importance of better understanding the gut microbiome. Histamine is a crucial chemical in the body, significantly affecting immune responses, gut health, and allergic reactions. Traditionally, it was believed that mast cells were the primary producers of histamine. However, recent studies reveal an intriguing discovery: the common environmental bacterium, Pseudomonas aeruginosa, can prompt neutrophils—another type of white blood cell—to produce large amounts of histamine.

Excess histamine generated by neutrophils with chronic P. aeruginosa infection could contribute to the narrowing of the airways observed in asthma, allergies, chronic bronchitis, cystic fibrosis, and other lung diseases. This finding sheds new light on histamine intolerance and its connection to the symptoms related to the airways and lungs.

Neutrophils: A Surprise in Histamine Production

Airway inflammation and constriction associated with the release of histamine is a hallmark of asthma and allergies. Mast cells are considered the main producers of histamine (*), but new research indicates that the common environmental bacterium Pseudomonas aeruginosa can induce neutrophils, a type of white blood cell, to produce and release very high levels of histamine as well(*). 

Gut Bacteria and Histamine Intolerance

The growing focus on gut health has highlighted how bacteria, including Pseudomonas aeruginosa, affect the digestive systems and immune responses and contribute to histamine intolerance. A healthy gut typically balances histamine production and histamine degradation. However, infections or bacterial imbalances involving Pseudomonas species, including Pseudomonas aeruginosa, can disrupt this balance, worsening symptoms for those with histamine intolerance.

How To Test For Pseudomonas aeruginosa

One of the most common tests that I use in my practice to help my patients uncover the hidden causes of their digestive symptoms is a functional stool microbiome test, like the GI MAP

Chronic GI symptoms, like bloating, gas, abdominal pain and cramps, nausea, constipation, diarrhea, brain fog, leaky gut, allergies, hormonal imbalance, and food sensitivities, may trace their origins to imbalanced gut microbes as a root cause.

Why Pseudomonas aeruginosa Is Difficult to Treat

This bacterium is noted for its antibiotic resistance, making infections challenging to treat. In the gut, the presence of Pseudomonas aeruginosa can complicate medical treatment if it contributes to infection or gut dysbiosis. But it’s not only its ability to resist antibiotics that makes this bacteria difficult to treat at times.

Pseudomonas aeruginosa is also capable of forming biofilms—complex aggregations of microorganisms that can adhere to surfaces like the intestinal lining.

You can learn more about biofilm disruptors here. This property can make it more resistant to immune responses and antibiotic treatment, contributing to persistent infections.

How Pseudomonas aeruginosa, A Histamine Producing Bacteria, Affects Gut Health

Histamine is a biogenic amine that acts as a chemical messenger in the body, playing critical roles in immune response, digestion, and the central nervous system- Think Brain-Gut Connection. Its impact on gut health is multifaceted. Histamine-producing bacteria in the gut can significantly impact gut health, particularly for individuals with histamine intolerance, MCAS, or other digestive sensitivities. Here’s how histamine-producing bacteria are tied to gut health.

1. Histamine Production:

   – Certain bacteria in the gut can produce histamine as a byproduct of their metabolic processes. These include species like Enterobacter, Lactobacillus, H.pylori, Candida, Morganella, Escherichia coli, and Pseudomonas aeruginosa. This is why you don’t want to take just any kind of probiotic. Taking the wrong kind of gut bacteria for your gut could potentially exacerbate histamine intolerance. Here are a few histamine-lowering probiotics or histamine-neutral probiotics that I recommend.

2. Potential for Dysbiosis:

   – An imbalance in the gut microbiome, known as dysbiosis, can occur when histamine-producing bacteria outnumber the histamine-degrading bacteria.

   – This can lead to an excessive production of histamine, overwhelming the body’s capacity to break it down, especially if there’s a DAO deficiency, the enzyme that degrades histamine in the gut.

3. Interaction with the Immune System

   – Histamine plays a role in immune function and inflammation. Excess histamine production by gut bacteria can contribute to heightened inflammatory responses.

   – This can exacerbate conditions like Leaky Gut, SIBO,  irritable bowel syndrome (IBS), or inflammatory bowel disease (IBD).

How Gut Bacteria Cause Histamine Intolerance

Histamine intolerance is a condition where the body experiences adverse reactions due to an inability to effectively break down histamine, a compound involved in allergic reactions and immune response. The gut microbiota plays a significant role in this process, influencing how histamine is produced, metabolized, and regulated in the body. Here’s how gut bacteria contribute to histamine intolerance:

1. Histamine-Producing Bacteria:

   -Certain gut bacteria can produce histamine from amino acids such as histidine found in protein-containing foods. When these bacteria proliferate, they can increase histamine levels, potentially overwhelming the body’s ability to break it down. Other gut bacteria possess enzymes like diamine oxidase (DAO) and histamine-N-methyltransferase (HNMT), responsible for breaking down histamine. Bacteria such as Lactobacillus and other species found in fermented foods can contribute to increased histamine production.

2. Imbalance in the Gut Microbiome:

   – Dysbiosis, or an imbalance in the gut microbiome, can lead to an overabundance of histamine-producing bacteria or a decrease in beneficial bacteria that help degrade histamine. This imbalance can impair the body’s ability to maintain histamine homeostasis. Conditions like SIBO (dysbiosis of the small intestines) can lead to histamine intolerance.

3. Breakdown Enzyme Production:

   – The small intestine produces an enzyme called Diamine Oxidase (DAO), which is crucial for breaking down dietary histamine. Certain gut conditions or imbalances, such as inflammatory bowel diseases, can reduce DAO production or activity. Additionally, certain gut bacteria might compete for resources needed for DAO function or directly inhibit DAO, worsening histamine intolerance. Here’s How you naturally activate the DAO enzyme.

4. Microbial Influence on Gut Lining:

   – Leaky Gut can lead to histamine intolerance. Gut bacteria interact with the gut lining and immune system. An unhealthy gut microbiome might lead to increased intestinal permeability (“leaky gut”), allowing more histamine to enter the bloodstream and exacerbate intolerance symptoms.

5. Metabolite Production:

   – Gut bacteria produce a variety of metabolites, some of which can influence histamine metabolism and histamine production. These metabolites can impact intestinal health and immune function, thereby affecting histamine levels.

6. Impact of Diet and Probiotics:

   – Foods can influence the gut microbiome composition. A diet high in prebiotics and probiotics may support the growth of gut bacteria that help manage histamine levels. Conversely, foods high in histamine or that weaken the gut microbiome can exacerbate histamine intolerance.

Functional Medicine Approach To Managing Histamine-Producing Gut Bacteria

Functional medicine approaches histamine intolerance by addressing the root causes and utilizing natural strategies to manage and alleviate symptoms. Here’s an overview of how functional medicine practitioners might address this condition (this is just an overview)

 1. Comprehensive Assessment

Functional medicine practitioners conduct a detailed assessment to identify underlying factors contributing to histamine intolerance. This includes evaluating:

– Gastrointestinal health: Evaluating gut health, as issues like H.pylori, SIBO (Small Intestinal Bacterial Overgrowth), dysbiosis, and leaky gut can contribute to histamine intolerance (*).

– Liver function: Ensuring proper liver detoxification, as the liver plays a crucial role in breaking down histamines.

– Genetic predispositions: Genetic testing to assess mutations in genes responsible for histamine breakdown, such as the DAO (diamine oxidase) and HNMT (histamine-N-methyltransferase) genes.

2. Dietary Modifications

One of the primary strategies is adjusting the diet to reduce high-histamine foods while ensuring nutritional balance. This might involve:

– Elimination of high-histamine foods: This includes aged cheeses, fermented foods, alcoholic beverages, smoked meats, and certain nuts and fish. Learn more about the foods you want to avoid on a low-histamine diet here.

– Inclusion of fresh, low-histamine foods: low-histamine foods may include things like fresh meat and poultry, fresh fruits (except strawberries, avocados, and tomatoes), and fresh vegetables (except spinach and eggplant). Learn more about foods you should eat on a low-histamine diet here.

– Testing for food sensitivities: Food allergies and food sensitivities can cause an increase in histamine symptoms. IgE reactions (from food, mold, etc can trigger mast cells to produce histamine, tryptase, and prostaglandins. All chemicals that promote more inflammation.

3. Supporting Histamine Breakdown

Functional medicine emphasizes enhancing the body’s ability to metabolize histamines by:

– Supplementing with DAO enzyme: Some individuals benefit from DAO enzyme supplements to better manage histamine levels.

– B Vitamins: Vitamin B6 can support DAO function and histamine metabolism.

– Probiotics: Focusing on probiotic strains that do not produce histamine, such as Bifidobacterium infantis and Lactobacillus rhamnosus GG.

4. Gut Health Optimization

Improving gut health is a cornerstone of functional medicine, especially when patients have Pseudomonas and Histamine intolerance.

– Addressing dysbiosis or infection: Identifying and treating H.pylori, bacterial overgrowth, or yeast infections that may contribute to excess histamine (*), (*).

– Enhancing the gut barrier: Using supplements like L-glutamine and Zinc Carnosine to repair and fortify the gut lining.

– Anti-inflammatory strategies: Reducing intestinal inflammation through diet and supplements like omega-3 fatty acids and curcumin. Learn more about some of my favorite supplements when it comes to inflammation.

5. Liver and Detox Support

Support of liver detoxification pathways may be achieved through:

– Antioxidants: Including vitamins C and E, which can help quench oxidative stress and support detox pathways.

– Herbs such as milk thistle, Calcium D Glucarate, NAC, alpha lipoic acid, MSM, Artichoke: To aid liver function and promote healthy metabolism of histamines. If you are looking for a great Supplement to Detox your Liver Pathways, Check This Dual Tox- DPO out it supports both phase I and Phase II detoxification with one supplement

6. Stress Management

Recognizing the role of stress in exacerbating gut issues, functional medicine practitioners may recommend testing stress hormones, including neurotransmitters that influence our Gut motility.

7. Personalized Approach

Finally, functional medicine emphasizes a personalized approach, tailoring interventions based on individual genetic, environmental, and lifestyle factors. By taking a holistic, personalized approach to histamine intolerance, functional medicine aims to not only alleviate symptoms but also restore balance and enhance overall health. This integrative approach focuses on treating the whole person rather than just managing symptoms.

What You Should Remember About Hisamine and Pseudomonas aeruginosa and Histamine Intolerance

In conclusion, understanding the intricate relationship between histamine, Pseudomonas aeruginosa, and histamine intolerance is crucial for managing symptoms effectively. Recognizing the role that gut bacteria can play in influencing histamine levels offers new insights and potential strategies for those suffering from histamine intolerance.

It’s important to adopt a comprehensive approach that includes dietary modifications, lifestyle changes, and potentially probiotic supplementation to support a healthy gut microbiome. By staying informed and proactive, individuals can take meaningful steps towards improved health and well-being, reducing the impact of histamine intolerance on their daily lives.

1. DAO supplements for Histamine Intolerance and MCAS
2. Why Gut Dysbiosis is Such A Problem for People With Histamine Intolerance
3. The Best Probiotic Supplements to Lower Histamine Levels: Histamine-Lowering Probiotics
4. Histamine Intolerance Gut Health and SIBO- Another Piece Of The Puzzle

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