Irritable Bowel Syndrome (IBS) is one of the most common digestive conditions, yet it is also one of the most misunderstood. For many people, being told they have IBS feels vague and frustrating. It can sound like a “catch-all” diagnosis when nothing else explains their symptoms. If you have ever been told you have IBS and left thinking “But what does that actually mean?”, you’re not alone.
In this blog, I want to discuss what IBS really is, the different types, and how it links with the nervous system and histamine intolerance. I’ll also connect this with some of the topics I’ve covered in earlier blogs, including visceral hypersensitivity, stress, SIBO, and constipation. By understanding IBS more clearly, you’ll be better placed to make sense of your own symptoms and take practical steps toward feeling better.
What IBS really is
IBS is called a functional gut disorder. That means there isn’t a clear structural issue that shows up on scans or blood tests, but the way the gut functions isn’t working as it should. The nerves, muscles, and gut–brain communication can all play a part.
It’s important to know that IBS is real. Just because it doesn’t appear on an X-ray or colonoscopy doesn’t mean your symptoms are “all in your head”. The gut and nervous system are deeply linked, and IBS highlights just how sensitive and reactive that connection can be.
Many people describe IBS as unpredictable. You may feel fine one day and then suddenly bloated, crampy, or urgently needing the toilet the next. This lack of consistency makes IBS particularly disruptive to daily life, social plans, and confidence.
The Different Types of IBS
IBS is not the same for everyone. Doctors classify it into four main types, depending on the pattern of bowel movements:
- IBS-C: constipation-predominant. Stools are hard and infrequent, often leaving you feeling uncomfortable, heavy, and bloated.
- IBS-D: diarrhoea-predominant. Stools are loose and urgent, sometimes with cramping and unpredictability that makes daily life stressful.
- IBS-M: mixed type. A frustrating mix of constipation and diarrhoea, which can swing back and forth, often leaving you unsure what to expect.
Understanding your type of IBS matters because the triggers, management strategies, and even the nervous system responses can vary. For example, constipation can worsen visceral hypersensitivity, while diarrhoea is often linked more strongly to stress.
The role of Visceral Hypersensitivity
In my recent blog on visceral hypersensitivity, I explained how people with IBS often have a heightened sensitivity to normal gut sensations. For example, what feels like a small amount of gas in one person may feel like painful bloating in someone with IBS.
This sensitivity comes from the way the gut’s nerves and the brain interpret signals. It’s not that you’re imagining it, your body is genuinely experiencing more intense messages. This explains why bloating, cramping, or even a “creepy-crawly” feeling in the gut can feel so overwhelming.
Visceral hypersensitivity also explains why IBS symptoms can flare with stress, hormonal changes, or diet shifts. Your gut’s “alarm system” is more finely tuned, so triggers that wouldn’t normally cause discomfort can suddenly feel extreme.
Stress and the Nervous System
I’ve also written about the impact of stress on digestion, and this is especially important for IBS. Read more about the link between stress and histamine intolerance here.
The gut and brain are in constant communication via the vagus nerve. When you’re stressed or anxious, your body moves into “fight or flight” mode, and digestion is no longer a priority. This can slow things down (leading to constipation) or speed them up (causing diarrhoea).
Over time, repeated stress can keep your nervous system stuck in a dysregulated state. This makes your gut even more reactive and symptoms harder to control. Many people notice that their IBS flares during busy work periods, after emotional challenges, or even when they’re simply anticipating stress.
Learning ways to calm your nervous system, such as breathing techniques, mindfulness, brain retraining, gentle exercise, or vagus nerve stimulation, can be a powerful step in managing IBS. Tools such as hypnosis have been shown to reduce IBS symptoms. However, it’s not about the symptoms being “all in your head”. It’s about recognising how real the gut–brain connection is and supporting both sides of the equation.
SIBO and Constipation: Pieces of the puzzle
In previous blogs, I’ve also talked about SIBO (small intestinal bacterial overgrowth) and constipation. Both can overlap with IBS, and sometimes people are misdiagnosed with IBS when these are the underlying issues.
- SIBO occurs when bacteria build up in the small intestine, causing gas, bloating, pain, and altered bowel habits. This can look very much like IBS, however, sibo requires specific testing and treatment. People with SIBO often report excessive bloating after even small meals, or feeling like food “sits” in the stomach. Here are two articles that go into more depth about sibo – Is SIBO causing your histamine intolerance, The 3 Types of SIBO.
- Constipation, as I explained in my blog on the topic, isn’t just an inconvenience. It can feed into IBS-C by increasing pressure, changing gut bacteria balance, and heightening discomfort. Long-term constipation also increases the risk of visceral hypersensitivity, making the gut more reactive. Read more about constipation here.
Understanding whether your symptoms are purely IBS or linked to these conditions can help in choosing the right approach.
The role of gut bacteria in IBS
IBS isn’t just about sensitivity and nervous system regulation; research shows that imbalances in the gut microbiome (too many “unhelpful” bacteria, not enough diversity, or an overgrowth in the wrong place) are often part of the picture. Dysbiosis can:
- Drive gas and bloating through excess fermentation.
- Disrupt normal bowel patterns (constipation, diarrhoea, or swings between both).
- Increase gut permeability (“leaky gut”), which can make the gut lining more reactive.
- Interact with histamine intolerance, since some gut bacteria actually produce histamine.
Histamine Intolerance and IBS
Another important piece of the puzzle is histamine intolerance. Histamine is a chemical involved in immune responses, but it also affects digestion, sleep, and energy. Some people struggle to break down histamine properly, leading to symptoms like headaches, flushing, a runny nose, and gut problems.
For those with IBS, histamine intolerance can make symptoms worse. High-histamine foods, stress, and even hormonal changes can all increase histamine load, further aggravating the sensitive gut–nervous system connection.
This means that for some people, simply identifying and reducing high-histamine foods, or supporting the body’s ability to break histamine down, can make a real difference to their IBS symptoms. This is especially true for those who feel their gut reacts unpredictably to certain foods even after other causes have been ruled out.
IBS, Pain and Mast Cells
Mast cell activation is also connected with IBS symptoms. People with IBS often have mast cells in the gut that are extra sensitive. These cells sit right next to the nerves in your intestines, so when histamine is released, either from food or from your own body, it can easily set those mast cells off. Once “activated,” they can signal the brain and trigger pain.
Researchers have wondered whether people with IBS simply have more mast cells than average. The findings have been mixed—some studies show higher numbers, while others don’t. But a recent systematic review pulled all the evidence together and found something even more interesting: regardless of how many mast cells are present, those with IBS consistently have more activated mast cells compared to people without IBS!
IBS is not “Just in Your Head”
One of the hardest parts of living with IBS is feeling misunderstood. Because IBS doesn’t show up on traditional medical tests, many people are left feeling brushed off or told to “just reduce stress”. While stress is a factor, it’s not the whole story.
IBS is a genuine, multifactorial condition. It involves nerves, muscles, bacteria, diet, hormones, and the way the brain and gut communicate. Each person’s triggers are unique, which is why cookie-cutter advice often fails.
Putting it all together
IBS is not a single condition with a simple cause. It’s a complex interaction between your gut, nervous system, stress, bacteria, and even histamine. This is why it can feel so frustrating to manage, there isn’t a “one size fits all” solution.
The good news is that once you understand the different factors at play, you can start to identify which ones matter most for you. That might mean calming the nervous system, addressing SIBO or constipation, reducing histamine load, or building resilience to stress.
Working with a practitioner who understands the bigger picture can help piece the puzzle together. That way, your plan is tailored, not generic, and addresses the root causes of your symptoms.
If you’re living with IBS, remember: your symptoms are valid, your discomfort is real, and support is available. You don’t have to navigate this confusing condition on your own.
As I’ve shared across my blogs from visceral hypersensitivity to stress, SIBO, and constipation, the more we understand the “why” behind gut symptoms, the more empowered we are to take practical steps forward. IBS is not “just in your head”. It’s a mind–body condition that deserves compassionate care and a holistic approach. You don’t have to have a histamine issue to have IBS, and you don’t have to have IBS to have histamine issues. Either way, we can help you to regulate your nervous system, restore your gut microbiome and live a life without symptoms.
Struggling to get answers about your histamine intolerance symptoms?
Watch my free Masterclass – The 5 Steps to Healing from Histamine Intolerance.
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References
- Barbara G, Stanghellini V, De Giorgio R, Cremon C, Cottrell G, Santini D, et al. Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome. Gastroenterology 2004;126(3):693-702.
- Bashashati M, Moossavi S, Cremon C, et al. Colonic immune cells in irritable bowel syndrome: a systematic review and meta-analysis. Neurogastroenterol Motil. 2018;30:01.
- Guy E. Boeckxstaens. The Emerging Role of Mast Cells in Irritable Bowel Syndrome. Gastroenterology & Hepatology (N Y). 2018; Apr; 14(4): 250–252.
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