October 28, 2017 9:00 pm


Medical researchers are increasingly focusing on the role of mast cell activation and bacteria.

Firstly, we recognise mast cells’ role in inflammation, allergies, and lectins.

However, mast cells also play a crucial role in defending against and clearing infections.

Moreover, research shows that pathogenic bacteria activate mast cells to produce an anti-bacterial response.

Unfortunately, this natural function of mast cells has largely been overlooked.

Nevertheless, two recent papers shed light on bacteria’s impact on mast cells. The first, co-authored by Theoharides, highlights how bacteria affect mast cells. The second is a detailed Swedish review of the role of mast cells in bacterial infections, which led me to update this post in November 2017.

Finally, these papers reflect my observations in clinical practice, where infections are a leading cause of mast cell activation. Here is a brief overview.

Bacteria and Mast Cells

Mast cells are part of our immune system.

Firstly, they act as sentries, stationed predominantly in the skin, the airways, and the intestines—essentially, wherever our body meets the environment.

Then, when bacteria stimulate them, mast cell activation produces a range of mediators as a protective measure that causes a range of symptoms.

Consequently, mast cells are perfectly designed for this role.

Therefore, from a functional perspective, the question is not so much, “How do we suppress the mast cell from acting this way?” but rather, “What is the mast cell trying to respond to?”

Mast Cell Activation,

Mast Cell Activation Syndrome

Mast cell activation syndrome is a very common condition.

Firstly, syndromes are not really “diseases.” Specifically, the body’s cells have not stopped working. Instead, they represent a pattern of symptoms as the body adapts to stressors. Consequently, removing the stressor often resolves the syndrome.

Furthermore, rather than being one heterogeneous disease, mast cell activation syndrome is an umbrella term that encompasses significant variance in mast cell response depending on the trigger.

Moreover, any adverse stimulus, not just bacteria, can cause mast cell activation.

This is one reason why I like to use autonomic response testing: so that I can see all the stressors that our cells are trying to deal with both extracellularly and intracellularly.

Protective Mast Cells and Bacteria

A landmark 1996 study showed that mast cells are crucial for protecting against pathogenic bacteria.

Helicobacter pylori stands out among these bacteria. They are present in around 50% of the world’s population and are common in my clients. Fortunately, they can be easily treated with herbal remedies, even in the most sensitive individuals.

Moreover, there is strong evidence that bacterial toxins cause mast cell activation. These toxins are part of the bacteria’s cell wall and are released when the bacteria die.

Additionally, biofilms can release toxins, further triggering mast cell activation. Biofilms are protective layers bacteria form to shield themselves from the immune system and treatments. 

Therefore, addressing bacteria can significantly reduce mast cell activation, even in the most sensitive individuals.

Dysfunctional Mast Cells and Bacteria

While strong evidence shows that mast cells protect against bacterial infections, some studies reveal that mast cell activation can also exacerbate bacterial attacks.

For instance, a landmark 2010 study demonstrated that mast cells can be either protective or harmful, depending on the severity of the bacterial infection.

As the infection worsens, the body switches to other defences, like interleukin-4, to fight the bacteria. In simple terms, the body sacrifices the function of mast cells for stronger defenses.

Furthermore, there is strong evidence that some bacteria can mess with mast cells to weaken their effectiveness and increase the bacteria’s ability to cause disease.

In my view, this clearly shows the importance of getting rid of the harmful bacteria or addressing the root cause, rather than just trying to control mast cell activation.

Mast Cell Activating Bacteria

The GI-MAP test is a valuable tool for identifying bacteria that can activate mast cells, helping to address underlying causes of mast cell activation syndrome. It tests for the following mast cell-activating bacteria:

  • Helicobacter pylori: Known for its role in gastric issues and its ability to deplete essential vitamins and minerals, which contribute to mast cell activation.
  • Enterococcus faecalis: A common gut bacteria that, when overgrown, can trigger mast cell responses.
  • Pseudomonas aeruginosa: An opportunistic pathogen that can cause infections and activate mast cells.
  • Staphylococcus aureus: Frequently associated with skin infections and capable of activating mast cells.
  • Streptococcus species: Linked to throat infections and capable of triggering mast cell activation.
  • Candida species: Yeast overgrowth can provoke mast cell activation and exacerbate symptoms.
  • Candida albicans: A specific strain of Candida known to cause significant mast cell activation.
  • Lipopolysaccharide producers (gram-negative bacteria): release toxins that can significantly activate mast cells, leading to chronic inflammation and other symptoms.

By identifying these specific bacteria, the GI-MAP test provides crucial information for tailoring treatments to reduce mast cell activation and improve overall health.

Invasion of Mast Cells by Bacteria

Research has shown that many pathogenic bacteria can invade mast cells, increase their chances of survival, and replicate inside the cells.

Once inside the mast cells, these bacteria are less likely to be cleared, more likely to cause chronic infections, and more likely to alter mast cell behaviour, including mast cell activation and turnover.

Furthermore, standard testing panels often fail to detect intracellular bacteria since they are not easily found in urine, blood, or stool tests.

This is one reason I use autonomic response testing which can detect intracellular infections.

Therefore, understanding these detection methods and the impact of intracellular bacteria on mast cell activation is crucial for restoring health.


Much of the medical focus has been on mast cells and the mediators they release.

Consequently, this emphasis has led to extensive discussions about anti-inflammatory and mast cell-stabilizing substances. While these treatments are helpful, they are little more than a band-aid.

From a functional health perspective, the issue is not whether the mast cell is causing a chemical cascade but rather what is triggering that cascade. Therefore, this blog post outlines the link between pathogenic bacteria and mast cell activation.

Moreover, although there is still much to learn, mainstream medicine’s growing interest in the link between bacteria and mast cell activation is encouraging.

You can learn more about bacteria and histamine intolerance on the blog post, Histamine Producing Gut Bacteria.

Follow me on Instagram and Facebook to continue the conversation.

Additional Reading

Conti, Pio, et al. “Link Between Mast Cells and Bacteria: Antimicrobial Defense, Function, and Regulation by Cytokines.” Medical Hypotheses (2017).

Johnzon, Carl-Frederick et al “The role of mast cells in bacterial infection.” The American journal of pathology 186.1 (2016): 4-14.

Dahdah, Albert, et al. “Mast cells aggravate sepsis by inhibiting peritoneal macrophage phagocytosis.” The Journal of clinical investigation 124.10 (2014): 4577.

Matsuguchi, T. “Mast cells as critical effectors of host immune defense against Gram-negative bacteria.” Current medicinal chemistry 19.10 (2012): 1432-1442.

Gutiérrez Venegas, Gloria, et al. “Histamine promotes the expression of receptors TLR2 and TLR4 and amplifies sensitivity to lipopolysaccharide and lipoteichoic acid treatment in human gingival fibroblasts.” Cell biology international 35.10 (2011): 1009-1017.

Rönnberg, Elin, Bengt Guss, and Gunnar Pejler. “Infection of mast cells with live streptococci causes a toll-like receptor 2-and cell-cell contact-dependent cytokine and chemokine response.” Infection and Immunity 78.2 (2010): 854-864.

Piliponsky, Adrian M., et al. “Mast cell-derived TNF can exacerbate mortality during severe bacterial infections in C57BL/6-Kit W-sh/W-sh mice.” The American journal of pathology 176.2 (2010): 926-938.

Kulka, Marianna, et al. “Mast cells, which interact with Escherichia coli, up-regulate genes associated with innate immunity and become less responsive to Fc?RI-mediated activation.” Journal of leukocyte biology 79.2 (2006): 339-350.

Talreja, Jaya, et al. “Histamine induces Toll-like receptor 2 and 4 expressions in endothelial cells and enhances sensitivity to Gram positive and Gram negative bacterial cell wall components.” Immunology 113.2 (2004): 224-233.

Marshall, Jean S. “Mast-cell responses to pathogens.” Nature reviews. Immunology 4.10 (2004): 787.