When the reactions don't match the results
- 3 days ago
- 4 min read
Quick Summary: When Food Reactions Don’t Match Test Results
If you react to many foods but your food intolerance or gut health test shows near-normal results, the issue may be SIBO. Small Intestinal Bacterial Overgrowth (SIBO) can cause bloating, reflux, constipation or diarrhoea due to bacterial fermentation rather than immune activation. In these cases, food intolerance testing may appear normal because symptoms are driven by gas production in the small intestine, not antibody responses. Stool tests may also appear unremarkable, as SIBO is often an overgrowth of otherwise normal bacteria in the wrong location. Breath testing can help determine whether SIBO is contributing to your symptoms.
Could SIBO be the missing link behind your sensitive gut?
I remember when I first started working with food intolerance testing back in 2010.
For many patients, it was a game changer. A quick and practical way to identify foods contributing to daily bloating, gas, diarrhoea or eczema. It felt almost like magic. We could personalise a diet with clarity and people improved quickly.
Then came one patient I will never forget.
Chronic reflux. Diarrhoea. Intense bloating. Her doctors had already ruled out coeliac disease, parasites and inflammatory bowel disease. On paper, she was the perfect candidate for food intolerance testing.
So we tested.
Her results came back mild. Mostly normal.
She cried - and I understood her frustration.
Without an answer, she felt like she was back at square one.
But I didn’t see a dead end. Even then, I understood that minimal immune reactions often meant something else was driving the symptoms. Her reactions were likely not immune-based at all. They were almost certainly microbial.
At the time, we didn’t use the term SIBO widely. Breath testing was not common. Research was still emerging. I had to rely on clinical reasoning and experience.
She had to trust me.
Today, sixteen years later, the landscape has changed.
We now have validated breath testing. We have extensive microbiome research. We understand motility, fermentation and relapse patterns. And we can confidently identify and treat Small Intestinal Bacterial Overgrowth.
When Symptoms Feel Bigger Than the Results
Food intolerance testing measures immune responses to specific food proteins.
It is valuable. It identifies true immune-driven reactions. But not all food reactions are immune reactions. Some are driven by fermentation, enzyme insufficiency, altered motility or even genetic variants.
SIBO occurs when bacteria accumulate in the small intestine and ferment carbohydrates earlier than they should. This produces hydrogen and methane gas in a location (the small intestine) that is not designed to handle large volumes of fermentation (or bacteria).
The result?
Bloating
Reflux
Abdominal pressure
Constipation or diarrhoea
Feeling like you react to all food/drink
And because there is no immune-response triggering this reaction, food intolerance testing may appear minimal or even normal. Here's the kicker - even a stool test may appear normal. Because SIBO is not an infection - it is an overgrowth in the wrong place - and even healthy/normal microbes being present in the small intestine in high numbers can cause severe discomfort.
The test is not wrong. It is answering a different question.
Why You Start Reacting to More and More Foods
Many patients with SIBO notice a progression.
First, high sugar or processed foods make you uncomfortable - that glass of wine/dessert or a packet of chips is no longer tolerated. Then high FODMAP foods such as onions, garlic and apples need to be avoided. Then portion size becomes important. Then even low FODMAP foods may start causing discomfort. Or you may have a swollen belly from a single mint or a cup of coffee.
This is not because your body suddenly became intolerant to everything.
It is because bacterial load increased.
The more bacteria present in the small intestine, the more gas is produced from even small amounts of carbohydrate. Food becomes the fuel. Bacteria are the driver.
The Detect, Repair, Reintroduce Framework
At Food Intolerance Australia, my approach is simple but structured.
Detect: Identify any current trigger foods and assess for underlying imbalances such as SIBO/bacterial imbalances via breath and stool testing. Reduce foods that fuel overgrowth while stabilising symptoms.
Repair: Restore motility. Improve microbial balance. Strengthen the gut environment to reduce relapse risk.
Reintroduce: Systematically expand the diet and determine tolerance thresholds so you can eat confidently again. Yes, I want you eating cake, enjoying a glass of wine and going out for meals again, when the occasion calls for it.
Restriction is not the end goal - it's a short term tool. Resilience is the marker of success.
Signs you should be doing a SIBO test
You may want to investigate SIBO if:
You react to a wide range of foods
Bloating worsens as the day progresses
You have chronic constipation or unpredictable bowel habits
Low FODMAP helped initially but stopped working
Your food intolerance results do not match your lived experience of reacting to 'everything'
SIBO breath testing allows us to measure hydrogen and methane gas production and determine whether bacterial overgrowth may be present. Learn more about SIBO breath testing here.
For more complex presentations, comprehensive microbiome testing, combined with breath testing, provides deeper insight into bacterial balance, fungal markers, digestive function and inflammatory drivers.
The Bigger Lesson
That patient from 2010 taught me something important.
Sometimes the absence of immune reactivity is not a failure. It is direction.
If you feel stuck, confused, or frustrated by results that don’t explain your symptoms, the next step may not be further restriction. It may be broader investigation.
Because when the reactions don’t match the results, it is time to ask a different question.
And often, that question leads us to SIBO.
If you are reacting to everything, it may not be about eliminating more foods. It may be about identifying what is driving fermentation in the first place.
And once you identify the driver, the path forward becomes much clearer.
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Learn More About The Food Intolerance Australia SIBO Recovery Plan
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