IBS flare-up: Symptoms, causes, duration and treatment

What is an IBS flare-up?

An IBS flare-up is a temporary worsening of gut symptoms – cramping, bloating, and changes in bowel habits – that can last anywhere from a few hours to a few days, and almost always passes.

The terms ‘IBS flare-up and ‘IBS attack’ are often used interchangeably. Both describe a sudden worsening of symptoms – the difference is mainly intensity, with an attack typically referring to something more severe or prolonged. There is no clinical distinction between them.

Flare-ups can be triggered by stress, food, hormonal changes, or a gut infection – and sometimes they strike with no clear cause at all. Understanding what's driving yours, and what you can do when one hits, makes them much easier to manage.

What triggers an IBS flare-up?

Because IBS is a gut-brain disorder, triggers don't cause structural damage to the gut – they activate a nervous system that's already oversensitive. This is also why flare-ups can sometimes occur with no clear trigger at all.

Common triggers include:

Stress and psychological factors

Both short-term and chronic stress can heighten gut sensitivity and alter how the intestines move. Anxiety and depression also intensify gut-brain signaling – which is why emotional and digestive symptoms so often arrive together.1

High FODMAP foods

Fermentable carbohydrates – including fructans (garlic, onion, wheat), lactose (dairy), fructose (apples, honey, mango), and polyols (mushrooms, cauliflower, stone fruits) – are poorly absorbed in the small intestine and ferment in the gut, producing gas and triggering symptoms.

Hormonal changes

Many people with IBS notice symptoms worsen at certain points in their menstrual cycle, reflecting how sex hormones interact with gut-brain signaling.

Gut infections

Gastroenteritis or food poisoning can trigger a period of heightened gut sensitivity – sometimes developing into post-infectious IBS, where symptoms persist long after the infection has cleared.2

Caffeine and alcohol

Both can stimulate the intestines and lower the threshold for symptoms, particularly diarrhea and urgency.

Why IBS is a gut-brain disorder

IBS is not just a digestive condition – it is a gut-brain disorder, meaning the problem lies in how the gut and brain communicate rather than in any structural damage to the digestive tract.3

In people with IBS, this communication becomes dysregulated, making the gut oversensitive. Normal digestive activity – gas, movement, pressure – gets processed as pain or discomfort that most people would never notice. During a flare-up, this oversensitivity is at its peak, which is why symptoms can feel so intense and unpredictable even when nothing has visibly changed.

"Symptoms are very real and they are driven by what happens between the gut and the brain and the brain to the gut along what's called the brain-gut axis." – Dr. Megan Riehl, GI Psychologist, Clinical Director of the GI Behavioral Health Program at the University of Michigan

IBS is the most common gut-brain disorder, but it isn't the only one. Functional dyspepsia, reflux hypersensitivity, and other conditions share the same underlying mechanism – an oversensitive gut-brain connection that can drive flare-ups in similar ways.

This short video explains what a gut-brain disorder is, how the gut-brain axis works, and why IBS is considered a gut-brain condition.

Even in conditions like IBD and GERD, where there is a structural or inflammatory component, research suggests that gut-brain dysregulation often plays a role in ongoing symptoms – particularly when symptoms persist despite treatment.

This is why treatment approaches that calm the nervous system, rather than just managing symptoms in the moment, tend to produce the most lasting relief.

How long does an IBS flare-up last?

Most IBS flare-ups peak within 2–4 days and then ease on their own, though some can linger for a week or more depending on the trigger and how quickly you're able to address it.

Duration varies widely from person to person. Some people experience a sharp flare that resolves within hours; others find symptoms come and go in waves over several weeks.

A number of factors influence how long a flare-up lasts – including what triggered it, stress levels at the time, and whether you're able to make adjustments to your diet or routine while symptoms are active.

The good news is that flare-up duration tends to shorten with better management. People who understand their triggers, have strategies in place, and are actively working on the gut-brain connection through approaches like gut-brain therapy often find their flare-ups become less frequent and easier to recover from over time.

What are the symptoms of an IBS flare-up?

The most common symptoms of an IBS flare-up are abdominal cramping, bloating, and changes in bowel habits – though the experience varies widely between people and between episodes.

Abdominal pain and cramping

Often the most disruptive symptom, ranging from a dull ache to sharp spasms that come and go in waves.

Bloating and abdominal swelling

The abdomen can feel visibly distended and uncomfortable, often worsening as the day goes on.

Changes in bowel habits

This may mean diarrhea, constipation, or alternating between both – sometimes within the same flare-up.

Gas and urgency

Excessive gas and a sudden urgent need to use the bathroom are common, and can make flare-ups particularly hard to manage in daily life.

A sense of incomplete emptying

Many people feel they haven't fully emptied their bowels after going to the bathroom, which can add to discomfort and frustration.

Some people also notice symptoms beyond the gut during a flare-up – including fatigue, headaches, heightened anxiety, and difficulty concentrating. This reflects how closely the gut and brain are connected: when one is under stress, the other often feels it too.

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What to eat during an IBS flare-up

The best foods to eat during an IBS flare-up are low FODMAP – gentle on the gut, easy to digest, and unlikely to ferment and worsen symptoms when your gut-brain system is already on high alert.

FODMAPs are fermentable carbohydrates that are poorly absorbed in the small intestine. In people with IBS and other gut-brain disorders, they can trigger bloating, cramping, and changes in bowel habits – particularly during a flare when gut sensitivity is at its peak.4 Temporarily reducing high FODMAP foods while IBS symptoms are active can help calm things down faster.

Foods to avoid during an IBS flare-up

High FODMAP foods that commonly worsen IBS symptoms include onion, garlic, wheat, rye, apples, mangoes, watermelon, honey, cow's milk, yogurt, ice cream, chickpeas, lentils, mushrooms, and cauliflower.

Foods that are easier to tolerate

Gentler, low FODMAP options include white rice, basmati rice, gluten-free oats, chicken, fish, cooked carrots, potatoes, kale, and small portions of nuts like pecans and pine nuts.

"Because at the end of the day, food is celebratory. It's cultural. It brings joy. We don't want patients to feel like they have to stick with a really strict diet." – Morgan Binder, Physician's Assistant and Registered Dietitian, Arizona Digestive Health

A low FODMAP diet works best as a short-term tool during an IBS flare-up, not a permanent way of eating. The goal is to identify your personal triggers over time – not to restrict forever.

How to calm an IBS flare-up

The most effective way to manage an IBS flare-up is to combine short-term symptom relief with approaches that address the gut-brain connection directly – calming the nervous system, not just the gut.

Switch to low FODMAP foods temporarily

Switching to low FODMAP foods while symptoms are active gives the gut less to react to. This doesn't need to be permanent – just a short-term reset while the flare settles.