Bloating after fermented foods. Headaches after wine. Flushing, itching, diarrhea, congestion, or seemingly unpredictable reactions to foods that were previously well tolerated.
For some people, these symptoms may raise the question of histamine intolerance.
Histamine intolerance is generally understood as an imbalance between the amount of histamine entering or being produced in the body and the body's ability to break it down. Much of the conversation has historically centered on dietary histamine and the enzyme diamine oxidase (DAO).
But emerging research suggests another piece of the puzzle may deserve attention:
The gut microbiome itself.
Certain gut bacteria can produce histamine. Others interact with the intestinal environment in ways that may influence inflammation, barrier function, and potentially histamine metabolism.
This means histamine intolerance may not always be simply a story of eating "too much histamine."
It may also be a story about the microbial ecosystem in which histamine is being produced and metabolized.
First: What Is Histamine?
Histamine is a naturally occurring signaling molecule with important roles throughout the body. It participates in immune responses, gastric acid secretion, neurotransmission, vascular regulation, and other physiological processes.
Histamine isn't inherently harmful. The problem arises when histamine exposure or production exceeds an individual's capacity to metabolize it effectively.
In the intestine, one of the primary enzymes responsible for degrading extracellular histamine is diamine oxidase, or DAO. Reduced DAO activity can increase the amount of histamine available for intestinal absorption. DAO activity may be influenced by genetic factors, medications, diet and conditions affecting the intestinal mucosa.
When histamine accumulates, symptoms can vary considerably and may include:
- Bloating, abdominal pain or diarrhea
- Headaches or migraines
- Flushing or itching
- Nasal congestion
- Palpitations
- Dizziness
- Other allergy-like symptoms
Importantly, these symptoms are not specific to histamine intolerance, which is one reason diagnosis can be challenging.
Where Does the Gut Microbiome Come In?
Here's where things become particularly interesting.
Humans aren't the only ones capable of producing histamine.
Bacteria can produce it too.
Certain bacteria contain the enzyme histidine decarboxylase (HDC), which converts the amino acid histidine into histamine.
A large genomic analysis investigating more than 36,000 bacterial genomes identified 117 putative histamine-secreting bacterial species and found histamine-secreting bacteria distributed across multiple bacterial phyla.
This introduces an important concept:
The amount of histamine in the intestinal environment may be influenced not only by food and host metabolism, but also by the composition and activity of the microbial ecosystem.
And researchers have started finding differences in the microbiomes of people experiencing histamine intolerance.
People With Histamine Intolerance May Have Different Microbial Ecosystems
One particularly interesting study compared the intestinal microbiota of individuals with histamine intolerance symptoms with healthy controls.
Researchers found that the histamine-intolerance group had significantly lower levels of several bacteria commonly associated with intestinal health, including:
Faecalibacterium
Faecalibacterium prausnitzii
Ruminococcus
Prevotellaceae
At the same time, they observed greater abundance of several bacteria with histamine-producing potential, including:
Staphylococcus
Proteus
Enterobacteriaceae
Clostridium perfringens
Enterococcus faecalis
The authors proposed that an increased abundance of histamine-producing bacteria could potentially contribute to intestinal histamine accumulation and subsequent systemic absorption.
However, there is an important detail.
Fecal histamine concentrations were not significantly different between the histamine-intolerance and control groups.
That finding is a useful reminder of why microbiome science rarely comes down to a single organism—or even a single metabolite measured in stool.
It's Not as Simple as "Histamine-Producing Bacteria = Bad"
This distinction is critical.
Finding a bacterium capable of producing histamine does not automatically mean that organism is causing someone's symptoms.
Microbial histamine can have different biological effects depending on the bacterial strain, amount produced, surrounding microbial community, intestinal environment and host response. Research has described both pro-inflammatory and immunomodulatory effects of microbiota-derived histamine.
Even organisms we commonly think of as "beneficial" can complicate the picture.
For example, histamine-production capacity has been reported among strains or species belonging to organisms such as Lactobacillus and Bifidobacterium.
That doesn't make these entire groups "bad bacteria."
It illustrates something much more important:
Function can be strain-specific, and microbial behavior occurs within an ecosystem.
This is one reason simply creating a list of "histamine-producing bacteria" and trying to eradicate them may oversimplify the biology.
Could Dysbiosis Also Affect Our Ability to Break Down Histamine?
Potentially—and this may be one of the more interesting connections.
DAO is produced by intestinal epithelial cells. Conditions that affect the intestinal mucosa have been associated with reduced DAO activity, and researchers have proposed that microbial dysbiosis and mucosal inflammation could potentially interfere with normal DAO function.
This creates a possible bidirectional relationship:
Microbial ecosystem disruption
↓
Greater abundance/activity of histamine-producing organisms and/or altered intestinal environment
↓
Potential mucosal inflammation or dysfunction
↓
Reduced capacity to metabolize intestinal histamine
↓
Greater histamine exposure in susceptible individuals
But this should currently be viewed as a proposed biological model, not an established causal pathway.
The human evidence remains limited, and we do not yet know whether microbial changes cause histamine intolerance, result from it, or reflect other factors occurring simultaneously.
What About a Low-Histamine Diet?
Reducing dietary histamine can be useful for symptom management in some individuals, particularly while investigating potential contributors.
But long-term restriction shouldn't necessarily be the end goal.
A small pilot study followed five women with histamine intolerance undergoing dietary treatment for nine months. Researchers observed reductions in several histamine-secreting bacteria, including Proteus and Proteus mirabilis, alongside an increase in Roseburia.
Because this study included only five participants, it cannot establish that dietary treatment reliably remodels the microbiome or that these microbial changes caused symptom improvement.
It does, however, raise an interesting question:
Rather than only asking which high-histamine foods someone needs to avoid, should we also be asking why their tolerance to histamine may have changed in the first place?
What Can Microbiome Testing Tell Us?
A microbiome test cannot diagnose histamine intolerance.
There is currently no validated microbiome signature that can tell a clinician, "This patient has histamine intolerance."
What comprehensive microbiome testing can do is provide another layer of information about the intestinal ecosystem.
For someone experiencing suspected histamine-related symptoms, a clinician may want to understand:
- Which bacterial species dominate the ecosystem?
- Are potentially histamine-producing organisms elevated?
- Is there expansion of potentially disruptive organisms such as Proteobacteria?
- Are important butyrate-producing organisms represented?
- What does overall diversity and evenness look like?
- Is the ecosystem highly dominated or relatively balanced?
- Are there other patterns that could help contextualize the patient's symptoms?
This is where species-level resolution and whole-ecosystem interpretation become important.
Knowing that one potentially histamine-producing bacterium is present doesn't tell us enough.
The better question is:
What is happening in the ecosystem around it?
The GutID Ecosystem Approach
At GutID, we don't believe microbiome results should be interpreted as a list of "good" and "bad" bacteria.
Using Titan-1™ long-read ribosomal sequencing, GutID provides high-resolution bacterial identification designed to characterize the microbial community at the species level.
For a patient experiencing histamine-related symptoms, this allows clinicians to move beyond simply looking for one organism and instead examine the broader microbial environment.
The goal isn't to diagnose histamine intolerance from a stool sample.
It's to provide clinicians with better information about the bacterial ecosystem so they can integrate those findings with diet, symptoms, medications, medical history, DAO-related factors and the larger clinical picture.
Histamine Intolerance Is Another Reason Context Matters
Histamine intolerance illustrates one of the biggest lessons emerging from microbiome research:
Individual bacteria rarely tell the whole story.
Histamine can come from food, human cells and microorganisms. Our ability to metabolize it varies. Microbial production varies. And the biological effects of microbial histamine appear to depend on the organisms producing it and the ecosystem and host in which that production occurs.
We still have a great deal to learn about the microbiome–histamine relationship.
But rather than reducing the conversation to:
"Which bacteria produce histamine?"
A more useful question may be:
"What is happening within this microbial ecosystem that could be influencing histamine production, metabolism and tolerance?"
That's the shift from looking at individual organisms to understanding the ecosystem.
References
- Sánchez-Pérez S, et al. Intestinal Dysbiosis in Patients with Histamine Intolerance. Nutrients. 2022;14(9):1774.
- Mou Z, et al. The taxonomic distribution of histamine-secreting bacteria in the human gut microbiome. BMC Genomics. 2021.
- Sánchez-Pérez S, et al. The dietary treatment of histamine intolerance reduces the abundance of some histamine-secreting bacteria of the gut microbiota in histamine intolerant women: A pilot study. Front Nutr. 2022.
- De Palma G, et al. Histamine-producing bacteria and their role in gastrointestinal disorders. Expert Rev Gastroenterol Hepatol. 2023.
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