Why Does My IBS Come and Go? What Drives the Waves

IBS comes and goes because that is how the condition works. It is diagnosed on symptoms that recur rather than symptoms that never let up, diary studies show that loose stools, hard stools, pain and bloating arrive in clusters of a few days, and long-term studies show symptoms fading, returning and changing shape over years. Underneath those waves is a gut that is more sensitive than average and a nervous system that turns that sensitivity up and down with stress, sleep, hormones, infections and more.

None of that makes a bad week after a good month less demoralising. But it does change the question. Instead of "what did I do wrong?", the more useful question is "what moved my threshold?" This guide covers what the research says about the waves, which explanations have good evidence and which are guesses, and how to find a pattern in symptoms that seem to follow no rules at all.

Is it normal for IBS to come and go?

Yes. Coming and going is so typical of IBS that it is built into how the condition is defined and described.

The Rome IV criteria, which gastroenterologists use to diagnose IBS, require recurrent abdominal pain on average at least one day a week over the last three months, linked to bowel movements or to changes in stool frequency or form (Mearin 2016). "On average" and "recurrent" are doing a lot of work there. A review in The Lancet describes IBS as affecting 5% to 10% of people at any one time and running a relapsing and remitting course in most of them (Ford 2020).

Long-term studies show just how much movement there is. When researchers surveyed 1,365 people in Minnesota repeatedly over about 12 years, the overall rate of IBS in the community stayed fairly stable. Individual people, though, did not. Among those with gut symptoms at the start, roughly 20% had the same symptoms at follow-up, 40% had no symptoms and 40% had different symptoms (Halder 2007). A 10-year Icelandic study found the same turnover and described IBS as a cluster of symptoms that "float in time" between categories (Olafsdottir 2010).

Across population studies, the share of people whose IBS symptoms resolve at follow-up ranges from 17% to 55% (Yadav 2021). That is genuinely encouraging, but it comes with a caveat from the Minnesota data: many symptoms that "disappeared" had in fact been replaced by different ones.

In r/ibs, a post asking whether anyone else had months of flares followed by months of almost nothing drew replies describing every rhythm imaginable: week-to-week waves, month-long swings, and one person who went nearly a year without trouble before eight months of pain (r/ibs thread). The poster had already had a clear colonoscopy and was having further tests, which is the right order of things.

What do the waves actually look like?

The best evidence comes from people who logged every bowel movement for weeks. It shows that IBS symptoms do not scatter randomly across the calendar. They clump.

In a study of 124 people with IBS who recorded the Bristol stool type of each bowel movement and rated pain and bloating every day for up to three months, symptoms on one day strongly predicted symptoms on the next. That clustering showed up in stool form for 69% of participants, in pain for 52% and in bloating for 69%. The researchers could define clear episodes: diarrhoea episodes averaged 2.1 days, constipation episodes 4.5 days, pain episodes 3.1 days and bloating episodes 3.5 days (Palsson 2014).

Two findings from that study are especially useful if your symptoms feel chaotic:

• Pain often travels on its own. More than half of pain episodes happened outside episodes of abnormal stools. So a painful stretch with normal-looking stools is still consistent with IBS.
• An episode has momentum. Once a run of loose or hard stools starts, it tends to continue for a few days. That is one reason a single "bad" meal can seem to set off days of trouble, even when the meal was only the first domino, or not a domino at all.

Bowel habit also switches. In a 10-week study of 126 people with IBS, only 18% to 35% kept the same subtype every week, although most had one pattern that dominated at least 60% of the time (Engsbro 2012). In a larger trial cohort, only about one in four kept their original classification throughout, and mixed IBS was the least stable type (Yadav 2021). A widely upvoted r/ibs post about swinging from days of constipation to diarrhoea the next day drew hundreds of people recognising the same thing (r/ibs thread).

Why does a safe food feel fine one day and awful the next?

Usually because the food stayed the same and your gut did not. IBS involves a bowel that reacts more strongly than average to normal stretching, gas and movement, and how strongly it reacts moves around.

This is the core complaint of one of the most popular r/ibs posts on the subject: safe foods causing misery one day and nothing the next, until the poster felt they could no longer trust their own body (r/ibs thread). Several commenters described foods they had eaten for months or years suddenly becoming a problem.

The research explanation starts with how IBS works. Rome IV describes these conditions as disorders of gut-brain interaction involving a mix of altered gut movement, visceral hypersensitivity, changes in the gut lining and immune function, changes in gut bacteria, and altered processing of gut signals in the brain (Drossman 2016). The British Society of Gastroenterology guideline describes IBS as having been reclassified in exactly these terms (Vasant 2021).

Sensitivity matters a great deal. Across five patient groups totalling 1,144 people, gut symptom severity rose step by step with how sensitive people's bowels were to balloon stretching, even after accounting for anxiety and depression (Simrén 2018). A useful way to picture it is a threshold. Food, gas, stool and gut movement create signals. Whether those signals cross into pain or urgency depends on where your threshold sits that day.

Things that can lower the threshold, or add to the load, include:

• Stress. In a randomised trial in 21 healthy volunteers, an injection of a key stress hormone increased how much of a fructose drink escaped absorption and reached the colon (Murray 2016). That was not an IBS study, but it shows one way a tolerated food could behave differently in a stressful week.
• The rest of the day's food. A food that is fine alone can tip you over when it follows several other fermentable foods, and the reaction can surface hours or a day later. Our guide on how long after eating IBS flares up covers that timing in detail.
• Sleep, hormones and recent illness, covered below.

Researchers are also looking at whether fluctuations in immune activity in the gut lining explain some of the ups and downs, but the review that raises this calls the evidence emerging, and notes there is very little data on what drives changes in bowel habit (Yadav 2021). Anyone who tells you they know exactly why your IBS changes is overselling.

How much does stress explain?

Stress and IBS symptoms are closely linked, but the relationship is tighter in the moment and more two-way than the "stress causes flares" shorthand suggests.

The clearest data come from daily diaries. In a study of over 200 people with IBS who recorded stress and gut symptoms every day for four weeks, stress and symptoms in the same week were very strongly related. But stress in one week did not independently predict symptoms one or two weeks later once that same-week link was accounted for. The authors concluded the relationship looked reciprocal: stress worsens symptoms and symptoms add stress (Blanchard 2008).

A real-time study sharpened that picture. For seven days, 37 people with IBS and 36 healthy controls rated stress and pain at up to ten random moments a day on their phones. People with IBS did not report more stress than the controls, but their pain rose more when stress rose. Stress at one moment did not predict pain at the next (Vork 2020). In other words, the difference was not how stressed people were. It was how much their gut responded.

Longer-running, serious stress may matter for the bigger waves. In an older study of 117 outpatients followed for 16 months, none of those facing even one chronic, highly threatening life stressor improved by half, while everyone who did improve did so without such a stressor (Bennett 1998). It was a small study, so treat the size of the effect with caution.

The gut-brain link also runs in both directions over years. In a 12-year Australian population study, higher anxiety predicted developing gut disorders later, and having a gut disorder at the start predicted more anxiety and depression later (Koloski 2012). Across 73 studies, about 39% of people with IBS had anxiety symptoms and about 29% had depressive symptoms, roughly three times the odds seen in people without IBS (Zamani 2019).

In r/ibs, a post titled "There's no such thing as safe food if your trigger is anxiety" described a loop many recognised: worry about a flare, which brings on a flare, which brings more worry (r/ibs thread). Others in the thread said that when they felt mentally settled, they almost forgot they had IBS. That is not proof, but it fits the research well.

Can a bad night's sleep cause a flare the next day?

It can contribute, especially to pain. Sleep is one of the few factors where studies have looked specifically at the next day.

In 24 women with IBS who kept sleep and symptom diaries across a menstrual cycle and wore activity trackers, poorer self-reported sleep predicted more abdominal pain, anxiety and tiredness the following day, although not other gut symptoms. Symptoms, on the other hand, did not predict worse sleep that night (Buchanan 2014).

A second small study compared 24 people with IBS and 26 healthy controls over a week of wrist monitoring. People with IBS woke more often during the night, and more waking episodes went with worse abdominal pain and gut distress, but not with changes in bowel pattern. Part of the effect seemed to run through mood (Patel 2016).

Both studies were small, but the direction is consistent: a broken night is a reasonable suspect for a painful day. It is also one of the easiest things to note in a log, and one of the most often forgotten.

Do hormones and the menstrual cycle play a part?

For many women, yes. It is one of the most common explanations people give for their waves, and there is research support.

In a daily diary study across one menstrual cycle, women with IBS had symptoms that varied by cycle phase, and not only gut symptoms: other physical, sleep and mood-related symptoms shifted too, with the strongest cycle effects in physical and menstrual symptoms. The pattern was similar regardless of whether women used oral contraceptives or which bowel pattern they had (Heitkemper 2003).

In the r/ibs thread about feeling fine for days and then having a horrible flare, several of the most upvoted replies tied their bad stretches to ovulation or to the days around their period, with one person saying they had assumed they were imagining the link (r/ibs thread). If that sounds familiar, our guide on why IBS gets worse on your period goes into the details.

Why did my IBS start, or change, after a stomach bug?

A bout of gastroenteritis is the best established risk factor for developing IBS, and it can also explain a sudden shift in a pattern that had been stable (Ford 2020).

A meta-analysis of 45 studies, covering more than 21,000 people who had an infectious gut illness, found that about 10% met criteria for IBS 12 months later. The risk was roughly four times higher than in people without such an infection. It was higher again after parasite or protozoa infections, and more likely in women, in people given antibiotics during the illness, in those with anxiety or depression, and after more severe illness (Klem 2017). A Rome Foundation working team report puts the figure at about 10% too, and notes that the mechanisms, involving gut bacteria, the gut lining, serotonin signalling and the immune system, are still incompletely understood (Barbara 2019).

The practical point: if your symptoms changed after food poisoning, a trip abroad with an upset stomach, or a course of antibiotics, write that date down. It is useful context for your doctor, and it may explain why foods you used to eat without thinking suddenly feel different.

Does the season or the weather matter?

Possibly for some people, but the evidence is thin, and it would be misleading to say otherwise.

In a 1995 Australian survey of 262 people, 23% of those with IBS reported a moderate or greater seasonal change in their bowel symptoms, and people with IBS were more likely than those with milder bowel symptoms to report seasonal changes in pain or bowel habit. The link was partly explained by a tendency to experience more physical symptoms generally (Talley 1995). More recently, hospital records from Korea showed new IBS diagnoses peaking in autumn and summer, tracking temperature and humidity (Hong 2026). But that study counted new diagnoses, not symptom changes in people who already have IBS.

We could not find good studies on holidays, travel or weather changes and IBS flares. Seasons change a lot of other things at once, including sleep, daylight, routine, food, alcohol, travel and mood, so those are the more testable suspects in your own logs.

Common reasons IBS symptoms fluctuate

This table summarises the main explanations, how strong the evidence is, and what to write down if you want to test each one. None of these is an either-or; several often stack together.

Why does "track your triggers" end up blaming every food?

Because when symptoms swing on their own, some bad days will follow almost every food by chance. Without a way to separate coincidence from cause, the list only grows.

One of the top comments in the "no rules" thread described exactly this: years of following the "track your triggers" advice produced a list containing nearly every food, plus contradictions like being too hot and too cold, until the person gave up on tracking altogether (r/ibs thread). Another commenter, who had also stopped tracking, said the effort had started to feel like superstition and was adding more anxiety than it relieved. Both reactions are understandable. Here is why that happens, and why it is not a sign that patterns do not exist.

Natural waves create false culprits. If your symptoms run in multi-day episodes (Palsson 2014), then every food eaten at the start of an episode will look guilty. Eat a food on ten days, and a few of those days will land at the start of a bad stretch whatever you do.

The same waves create false successes. People usually try something new when they feel worst, and symptoms that are at a peak tend to drift back down on their own. This is visible in clinical trials: across 73 drug trials in IBS, 37.5% of people taking a placebo reported improvement (Ford 2010). Placebo researchers point out that a substantial part of that apparent response is simply spontaneous symptom variation (Enck 2020). The same thing happens at home. A new supplement or cutting out a food just as a flare was ending will feel like it worked.

Memory exaggerates the peaks. In a study that compared end-of-day diaries with ratings taken at random moments through the day, people with IBS rated their pain higher in retrospect, tending to report their worst moments rather than their average (Mujagic 2015).

Food fear makes it worse. A post in r/ibs about choosing not to eat because safe foods kept turning into trigger foods drew many replies from people who had developed a real fear of food, including some who went on to develop eating disorders. Commenters urged seeing a registered dietitian rather than restricting further (r/ibs thread). If shrinking your diet is starting to shrink your life, our article on whether the low FODMAP diet can lead to disordered eating is worth reading, and so is a conversation with your doctor.

The answer is not more vigilance. It is a fairer comparison: days after a food against days without it, over enough repeats to wash out the waves, with stress, sleep and cycle noted alongside. That comparison is what Clairop runs on the foods you log, and it deliberately waits for at least five meals with a food and five without, and corrects for the many comparisons it makes, before calling anything a trigger.

How to spot a pattern when symptoms seem random: a worked example

The way through apparent randomness is to zoom out from single days to weeks, and to log a few non-food factors as consistently as you log meals. Here is a made-up but typical example.

The situation. Sam, 34, has IBS with a mixed bowel habit. They have had three good weeks, then a week of cramping, bloating and loose stools, followed by several days of constipation. They are convinced something they ate caused it, and are about to cut out bread, onions and coffee all at once.

Step 1: log the basics, briefly, for six to eight weeks. Sam logs meals and the Bristol type of each bowel movement as they happen, rates pain and bloating from 0 to 10 when symptoms come on, and adds a quick evening note of stress (0 to 10), sleep quality and cycle day. It takes a couple of minutes a day. Rating symptoms close to when they happen avoids the peak-inflating effect of memory.

Step 2: look for episodes, not days. At the end of eight weeks, Sam colours each day on a calendar: green for low symptoms, amber for moderate, red for bad. Instead of random red days, there are three distinct runs of bad days, each lasting three to six days. That already matches what the research describes.

Step 3: check what the runs have in common. Food first. Bread appears on 35 of the 56 days, spread evenly across green and red stretches. Onion-heavy meals are slightly more common before red stretches, but only on four occasions, too few to judge. Then the non-food columns. Two of the three bad runs began within two days of a night rated 3 out of 10 or lower for sleep, both during weeks with a stress rating above 7. The third began two days after a large restaurant meal and a late night.

Step 4: resist the neat story. Eight weeks is still a small sample. Sleep and stress travelled together, so Sam cannot tell which mattered more. The onion signal might be real or might be chance.

Step 5: act on it sensibly. Rather than cutting three foods, Sam keeps eating normally and keeps logging. They take the calendar and notes to their GP, mentioning that the constipation stretches are new since a stomach bug last spring. The GP checks for red flags, confirms nothing has changed that needs investigating, and discusses options including support with sleep and stress. For the possible onion link, a referral to a dietitian means any food testing is done in a structured way rather than by guesswork.

The lesson is not that food never matters. It is that a pattern only becomes visible once the natural waves and the non-food factors are on the same page as the meals. For how the comparison logic works, and why sample size matters so much, see the method page.

Can anything make the good stretches longer?

There is no way to switch IBS off, but several approaches have evidence for reducing symptoms or how often they worsen, and they target the threshold rather than a single trigger.

• Regular routines. NICE advises regular meals, taking time to eat and not leaving long gaps between meals, as well as making time for relaxation (NICE CG61).
• Physical activity. In a randomised trial of 102 people with IBS, those coached to increase their activity improved significantly more on a standard symptom score than those who kept their usual routine, and fewer of them saw symptoms get worse during the study (Johannesson 2011).
• Gut-brain psychological therapies. The American College of Gastroenterology suggests gut-directed psychotherapy for overall IBS symptoms (Lacy 2021), and NICE lists cognitive behavioural therapy and hypnotherapy among the psychological options for persistent symptoms (NICE CG61). These therapies are aimed at the gut-brain loop that makes symptoms so changeable, not at persuading you it is imaginary.
• A structured, temporary diet trial if food is a genuine factor. The ACG recommends a limited trial of a low FODMAP diet (Lacy 2021). It works best as a short elimination phase followed by reintroduction, ideally with a dietitian, so you end up eating as broadly as possible rather than avoiding foods for good.

Medication decisions belong with your doctor. If something you already take seems to change your bowel habit, raise it at your next appointment rather than stopping it yourself. Rome IV even has a separate category for constipation that starts or worsens when opioid medicines are started or changed (Mearin 2016), which is a reminder that medicines are one of many things that can reshape your pattern.

Myths about IBS that comes and goes

Myth: "If it went away for months, it can't have been IBS." Long quiet spells followed by a return are typical. In long-term studies, symptoms commonly disappear and reappear or change form (Halder 2007, Olafsdottir 2010).

Myth: "A flare means I ate something wrong." Food is one input. Stress in the moment, poor sleep, the menstrual cycle and the natural momentum of symptom episodes all play a part, and more than half of pain episodes happen even when stools are normal (Palsson 2014).

Myth: "If a remedy helped during my last flare, it works." Symptoms at a peak tend to ease on their own. In IBS drug trials, over a third of people on placebo improve (Ford 2010), and part of that is natural variation (Enck 2020).

Myth: "My subtype is fixed." Most people with IBS change subtype at some point, even if one pattern dominates (Engsbro 2012).

Myth: "Stress-related symptoms aren't real." People with IBS in a real-time study did not feel more stressed than healthy controls. Their guts simply responded more strongly to the same stress (Vork 2020). That is a physical difference.

Myth: "Once you've been diagnosed, any new symptom is just IBS." Guidelines say new red flag symptoms during follow-up should prompt further investigation (NICE CG61). A diagnosis is not a reason to ignore change.

If you have Crohn's disease or ulcerative colitis

IBS-type symptoms are common in inflammatory bowel disease, and they come and go too. A meta-analysis found that about 39% of people with IBD had symptoms meeting IBS criteria, including about 35% of those thought to be in remission (Halpin 2012). Over six years of follow-up in 125 people with IBD, only a third never reported IBS-type symptoms, and around 15% had symptoms that fluctuated. Reassuringly, those symptoms were not linked to worse disease outcomes such as needing steroids or surgery (Fairbrass 2022).

The catch is that you cannot tell from symptoms alone whether a bad spell is IBS-type sensitivity or active inflammation. If you have Crohn's or UC and notice bleeding, more frequent or night-time bowel movements, new pain, fever or weight loss, contact your IBD team promptly. They can check inflammation with tests rather than guesswork. For food questions specific to colitis, see our guide on whether food can trigger a UC flare.

When should changing symptoms be checked again?

A new wave of familiar symptoms is expected in IBS. A new kind of symptom, or a lasting change in your usual pattern, is a reason to go back to your doctor, however long you have had the diagnosis.

A diagnostic review for clinicians points out that IBS symptoms can change over time, and that those fluctuations can make the condition seem more complicated than it really is (Lacy and Patel 2017). The same review lists warning signs that point away from IBS. Guidelines add that red flag symptoms appearing at any point during follow-up should prompt further investigation or referral (NICE CG61).

See a doctor promptly if you have:

• Blood in your stool, or black, tarry stools
• Unexplained weight loss
• Anaemia, or feeling unusually tired and breathless
• A lasting change in your usual bowel habit
• Bowel movements or pain that wake you from sleep
• Fever alongside gut symptoms
• A lump in your abdomen
• New or changing bowel symptoms after age 50
• A family history of bowel cancer, coeliac disease or inflammatory bowel disease

These draw on warning signs listed in clinical reviews and guidelines, including overt bleeding, night-time stools, unintentional weight loss, recent changes in bowel habit, an abdominal mass, age over 50 without previous bowel cancer screening, and a family history of IBD or colorectal cancer (Lacy and Patel 2017), and the symptoms for which NICE recommends a stool test to guide referral for suspected bowel cancer, including a change in bowel habit, iron deficiency anaemia and an abdominal mass (NICE NG12).

Some conditions that look like IBS are worth asking about specifically:

• Bile acid diarrhoea. A meta-analysis found that about 28% of people meeting criteria for IBS with diarrhoea had bile acid malabsorption on testing (Slattery 2015). One of the most upvoted posts in r/ibs came from someone who spent ten years with a diagnosis of IBS-D before testing showed bile acid malabsorption (r/ibs thread).
• Coeliac disease. Biopsy-proven coeliac disease is more common in people with IBS-type symptoms than in people without (Irvine 2017). NICE recommends coeliac antibody testing, along with a full blood count and inflammation markers, for anyone meeting criteria for IBS (NICE CG61).
• Inflammatory bowel disease. For people with diarrhoea, the ACG suggests a faecal calprotectin test to look for IBD, as well as coeliac testing (Lacy 2021). In r/ibs, one person described 14 months of what was treated as IBS-C, with weight loss and steadily shrinking food tolerance, before further imaging led to a Crohn's diagnosis (r/ibs thread). Weight loss and progressive change, not ordinary waves, were the signals.

In another thread, someone who had been symptom-free for two months described three weeks of pain, nausea and diarrhoea that nothing would settle, and several replies urged them to get checked rather than keep trying remedies (r/ibs thread). That is sound instinct. A flare that is much longer, more severe or different from your usual pattern deserves a conversation, not just endurance.

When you go, a summary of the past few weeks is far more useful than a description of your worst day: how long episodes lasted, stool types, any night-time symptoms, weight, and what else was happening. Clairop can produce a one-page report for that appointment, but a clear handwritten summary does the job too.

Finally, it is worth saying plainly: symptoms that come and go are not a sign that you are failing to manage IBS. They are what IBS does. The aim is not to explain every bad day, but to understand your own rhythm well enough to spot the factors you can influence, and the changes that need a doctor. For more on keeping a log that actually tells you something, browse our symptom tracking guides.