When It Looks Like Histamine…
But Isn’t: Could Hydrogen Sulphide Be the Missing Piece?
Not every reaction to food is caused by histamine.
Many people who believe they have histamine intolerance actually react more strongly to foods that increase hydrogen sulphide (H₂S) production in the gut. While the symptoms can look surprisingly similar, the underlying mechanisms are completely different.
Understanding the difference can help explain why low-histamine diets sometimes fail, why certain foods trigger symptoms despite being low in histamine, and why simply avoiding more foods rarely solves the problem.
“I Swear It’s Histamine”
This is a conversation I have regularly in clinic.
A client tells me they react to garlic, onion, legumes, cruciferous vegetables, wine, fermented foods, supplements, or seemingly random meals. They experience bloating, headaches, anxiety, itching, fatigue, poor sleep, brain fog or a racing heart.
Naturally, they’ve concluded histamine must be the culprit.
Sometimes they’re right.
But sometimes the pattern doesn’t quite fit.
One clue is that many of their biggest triggers aren’t particularly high in histamine at all. Instead, they tend to be foods rich in sulphur-containing compounds
This is where hydrogen sulphide enters the picture.
What Is Hydrogen Sulphide?
Hydrogen sulphide (H₂S) is a gas naturally produced by bacteria within the digestive tract.
Although hydrogen sulphide often gets a bad reputation, it isn’t inherently harmful. In healthy amounts, it helps maintain the gut lining, supports healthy blood flow within the digestive tract, contributes to normal inflammatory regulation and acts as an important signalling molecule throughout the body. The problem occurs when production exceeds the body’s ability to manage it.
Certain gut bacteria can produce large amounts of hydrogen sulphide from sulphur-containing compounds in the diet. Excess production may contribute to digestive and systemic symptoms that often resemble histamine reactions.
Which Gut Bacteria Produce Hydrogen Sulphide?
Hydrogen sulphide isn’t inherently “bad”. In fact, it’s a normal by-product of microbial activity in the gut.
The challenge arises when hydrogen sulphide-producing bacteria become overly abundant or particularly active.
Several groups of bacteria can contribute to hydrogen sulphide production, including:
These bacteria can utilise sulphur-containing compounds from foods such as meat, eggs, garlic, onions and cruciferous vegetables.
Importantly, the presence of these bacteria doesn’t automatically mean there’s a problem. Many are normal residents of a healthy microbiome.
What often matters more is the overall balance of the ecosystem. Factors such as reduced microbial diversity, altered gut motility, low fibre intake, digestive dysfunction or changes in diet can shift the microbiome towards greater hydrogen sulphide production.
This is one reason why two people can eat exactly the same meal and have completely different reactions.
Why The Symptoms Can Look So Similar
One reason hydrogen sulphide can be mistaken for histamine is that both affect many of the same systems within the body.
Both can influence the nervous system, inflammatory signalling, blood vessel function and gut activity. As a result, the symptoms can overlap considerably.
People may experience brain fog, headaches, fatigue, anxiety, sleep disturbances, digestive discomfort or a general sense that they react unpredictably to foods. In some cases, skin symptoms such as itching may also occur.
From a symptom perspective, it isn’t always obvious which mechanism is driving the reaction. That’s why I pay close attention not only to the symptoms themselves, but also to the foods that trigger them and the pattern in which they occur.
Not all gut-related symptoms cause gut symptoms.
Kate Troup Naturopath
When The Symptoms Extend Beyond The Gut
One of the reasons hydrogen sulphide can be difficult to identify is that the symptoms don’t always stay in the digestive tract.
While bloating, gas and food reactions are common, that’s not always what brings people into my clinic. Sometimes the main complaints are joint aches, muscle pain, fatigue, headaches or brain fog. Others simply describe feeling inflamed after eating or notice that their exercise recovery isn’t what it used to be. Because these symptoms don’t immediately point to the gut, many people never consider that their microbiome could be playing a role.
Clinically, I’ve seen some individuals notice a clear relationship between sulphur-rich foods and the onset of these symptoms. They may feel relatively well, then develop aching joints, increased fatigue or a general sense that their body is more inflamed after consuming foods such as meat, garlic, onion, eggs, large amounts of cruciferous vegetables, and even sulphur-rich mineral water in one case.
What’s particularly interesting is that some people don’t experience obvious digestive symptoms at all.
Their main complaint may be fatigue, headaches, joint pain, muscle aches or a general feeling of inflammation after eating certain foods. Because they aren’t particularly bloated or experiencing obvious bowel symptoms, they may never suspect that the gut could be involved.
This doesn’t necessarily mean the foods themselves are harmful. In fact, many sulphur-containing foods are incredibly nutritious.
Instead, it raises a more interesting question:
Why is one person’s body able to tolerate these foods easily while another experiences symptoms?
One possible explanation lies within the gut microbiome.
Hydrogen sulphide is not simply a waste product. It acts as a biological signalling molecule and can influence immune function, intestinal barrier integrity and inflammatory pathways. When production becomes excessive, it may contribute to symptoms that extend beyond the gut.
For this reason, when someone experiences digestive symptoms alongside joint pain, fatigue or unexplained inflammatory symptoms after eating certain foods, I don’t immediately assume histamine is the problem. I also consider whether excessive hydrogen sulphide production could be contributing to the picture.
The goal isn’t to avoid healthy foods forever. It’s to understand why those foods are triggering symptoms in the first place.
Why Some “Histamine” Foods Don’t Fit The Histamine Story
One of the clues that prompts me to think about hydrogen sulphide is when a person’s biggest triggers aren’t actually high in histamine.
Instead, they often react to foods such as meat, garlic, onion, leeks or cruciferous vegetables.
These foods are frequently grouped together under other dietary approaches such as low-FODMAP diets, but they also contain sulphur-containing compounds that can influence hydrogen sulphide production in the gut.
This doesn’t mean hydrogen sulphide is always the answer. However, when someone reacts strongly to these foods despite following a low-histamine diet, it raises the question of whether another mechanism could be involved.
Rather than asking, “What foods should I avoid?”, a more useful question is often:
“Why am I reacting to these foods in the first place?”
It’s Not Just Food
Sometimes the clues don’t come from food at all.
In clinic, I’ve occasionally seen people react to sulphur-containing supplements in much the same way that they react to sulphur-rich foods. Examples can include supplements containing taurine, methionine or N-acetyl cysteine (NAC).
Others report that whey protein powders trigger symptoms and assume they’re reacting to dairy, lactose or histamine. While those explanations can certainly be relevant in some cases, they may not always tell the whole story.
Whey proteins are naturally rich in sulphur-containing amino acids, particularly cysteine and methionine. For some individuals, this appears to increase symptoms that are more consistent with hydrogen sulphide production.
The reactions are often digestive rather than allergic. Instead of hives, flushing or obvious histamine-type symptoms, people may experience gut pain, cramping, bloating, excessive gas or loose stools. One clue I pay particular attention to is a sulphur or rotten egg smell to the gas, as this can sometimes indicate excessive hydrogen sulphide production in the gut.
A rotten egg smell to gas is one of the strongest clues that hydrogen sulphide may be involved.
Kate Troup Naturopath
When these reactions occur alongside sensitivity to foods such as garlic, onion, eggs and cruciferous vegetables, it can raise the possibility that hydrogen sulphide-producing microbes are contributing to the picture.
Of course, not everyone who reacts to whey protein or sulphur-containing supplements has a hydrogen sulphide problem. However, when a consistent pattern emerges across multiple sulphur-rich foods and supplements, it’s worth considering whether the issue is the sulphur load itself rather than histamine or dairy.
Histamine vs Hydrogen Sulphide: Clinical Clues
| Histamine More Likely | Hydrogen Sulphide More Likely |
|---|---|
| Aged cheeses | Garlic and onion |
| Wine and alcohol | Sulphur-rich foods |
| Fermented foods | Eggs |
| Leftovers | Cruciferous vegetables |
| Hives or raised welts | Itching without visible skin changes |
| Flushing | Significant bloating |
| Runny nose | Egg-smelling gas and altered bowel habits |
| Immediate reactions | Delayed digestive reactions |
One pattern I’ve noticed clinically is that histamine reactions often produce visible skin changes.
People may develop flushing, hives or raised red welts after scratching.
With hydrogen sulphide, itching can be surprisingly intense, yet the skin often looks completely normal.
It’s not diagnostic, but it can be a useful clue.
Why A Low-Histamine Diet Sometimes Doesn’t Work
If hydrogen sulphide is the primary driver, a low-histamine diet may provide only limited improvement.
Many people find themselves progressively removing more foods while never achieving lasting symptom resolution.
In these situations, the issue may have little to do with histamine itself. More often, I start thinking about the broader gut ecosystem, including microbial imbalances, excessive hydrogen sulphide production, reduced microbial diversity and underlying digestive dysfunction. In these situations, identifying the root cause becomes far more valuable than endlessly expanding a food avoidance list.
Can Testing Help?
Symptoms alone cannot determine whether histamine or hydrogen sulphide is responsible.
Comprehensive microbiome testing can sometimes reveal patterns associated with excess hydrogen sulphide production, altered microbial balance or broader dysbiosis.
Combined with a person’s symptom history and food triggers, this often provides a much clearer picture than trial-and-error elimination diets.
The Bottom Line
Histamine intolerance is real.
But it isn’t always the answer.
If you’ve removed high-histamine foods and still react to garlic, onion, eggs, cruciferous vegetables or seemingly healthy foods, it may be worth considering whether hydrogen sulphide is playing a role.
The goal isn’t simply to identify the next food to avoid.
The goal is to understand why your body is reacting in the first place.
Because when we identify the underlying mechanism, we can start working towards restoring tolerance rather than continually restricting your diet.
