Why Does My IBS Get Worse in the Summer?

Summer probably is not doing one thing to your gut. It is doing six things at once, and they arrive in the same week.

Heat moves blood away from your digestive organs and towards your skin so you can cool down. You lose fluid and salt through sweat. What is on your plate shifts towards fruit, ice cream, cold drinks and barbecue food. Routines and sleep break for holidays and hot nights. You move more. And bacterial gastroenteritis, the single best documented route into new or worse IBS, peaks in warm weather.

None of those is the same problem, and none of them is fixed by the advice most summer IBS articles give, which is "stay hydrated". This guide separates the six, says honestly which ones have evidence behind them and which are plausible reasoning, and shows you how to work out which apply to you before next summer.

The short answer: heat is one of six things summer changes at once

If you have noticed that your symptoms reliably get worse from June onwards, you are not imagining it and you are not alone. But "heat makes IBS worse" is a conclusion, and it skips the part that would actually help you, which is working out which of the six changes is doing the damage in your case.

Here they are, in rough order of how much evidence sits behind them:

1. Gastroenteritis exposure. The one with a clear seasonal signal and a clear link to IBS.
2. What you eat and drink. Summer shifts your intake towards fermentable sugars, alcohol, cold drinks and larger evening meals.
3. Fluid and salt losses. Measurable, and they change stool output.
4. Sleep and routine disruption. Documented to predict next-day symptoms in IBS.
5. Activity. More walking, more heat exposure while moving.
6. The direct physiology of heat on the gut. Plausible, mechanistically supported, never tested in IBS.

A recurring post in r/ibs asks the question in almost exactly those terms: one person noticed that four separate summers had put them in the GI clinic, and wondered whether it was diet or "just the heat and humidity" (r/ibs thread). The replies split down the middle. Some people said heat alone did it. Others pointed out they eat far more fruit and raw vegetables in summer, or that they travel, or that they walk for hours in cities they do not know. That split is the whole problem in miniature, and it is why a single answer does not exist.

What heat actually does to your digestive system

When you get hot, your body's first move is to send blood to the skin so heat can escape, and one of the places it takes that blood from is your abdomen. A review of cardiovascular control during heat stress describes the redistribution of blood flow away from the visceral organs as one of the established responses to passive heating, alongside skin vasodilation and a rise in cardiac output (Gravel 2021).

That redistribution is the starting point for what sports scientists call exercise-induced gastrointestinal syndrome. A comprehensive review of the field describes the causes as stemming primarily from splanchnic hypoperfusion, meaning reduced blood flow to the gut, and increased sympathetic drive. Downstream, that can produce intestinal cell injury, increased permeability, and impaired transit, digestion and absorption. Crucially for us, the review states that heat exposure during exercise can substantially worsen these disturbances, in proportion to how much exertional heat stress is involved (Costa 2020).

There is a controlled experiment behind that. Eight male cyclists completed the same 60-minute cycling task twice, once at 34.5C and 53% humidity and once at 20.2C. The hot trial produced markers of gastrointestinal damage that were about 69% higher than the temperate trial. Be careful with what came next, because it matters: circulating endotoxins, inflammatory markers and measured gut permeability did not change (Osborne 2019). So the honest reading is that an hour of hard exercise in the heat measurably stresses the gut lining without, in that study, opening the barrier or triggering inflammation.

Why should a gut that has no inflammation care about any of this? Because IBS is fundamentally a problem of gut-brain communication, and the mechanisms named in the standard clinical description are motility disturbance, visceral hypersensitivity and altered central processing of gut signals (Ford 2020). A gut with normal sensitivity can absorb a change in blood flow and sympathetic drive without you noticing. A gut that already reports its ordinary workings to your brain as pain has less headroom.

Some people with IBS genuinely feel heat more, and it is measurable

This is the finding almost no summer IBS article mentions, and it is the most interesting one.

Researchers applied controlled heat to the forearm and calf of 42 people with IBS-D, 24 people with IBS-C and 52 healthy controls, measuring the temperature at which heat first became painful and the temperature at which it became intolerable. Both IBS groups were significantly more sensitive than controls, at both sites, with no meaningful difference between the subtypes (Zhou 2009).

Then they clustered the IBS participants and found three distinct groups. About 17% had heat sensitivity that looked like a healthy control's. About 47% were moderately sensitive. And about 36% showed a very high degree of thermal hyperalgesia. That last group also had the highest scores on a bowel disease severity index.

Two things follow. First, "heat bothers me more than it bothers other people" is a documented phenomenon in IBS and not a character flaw. A commenter in one r/ibs thread wrote that they had thought they were imagining the link and found the thread comforting (r/ibs thread). Second, this was skin sensitivity to applied heat, not a measurement of how ambient temperature affects bowel symptoms. It explains why a hot day might feel more punishing. It does not by itself explain diarrhoea.

Humidity is what most people are actually describing

Ask an IBS community about summer and the word that comes back is humidity, not temperature. One person wrote that humidity, more than heat, left them exhausted after several days, and that the few public accidents they had experienced came after stretches of hot, humid weather (r/ibs thread). Another, in a tropical climate, described the same thing.

The physiology of why explains the perception, even though nobody has tested humidity against gut symptoms. Your primary route for shedding heat is evaporating sweat off your skin, and humid air slows evaporation down. Work on critical environmental limits for human thermoregulation makes the point directly: humid heatwaves affect health disproportionately because of the relative inability to cool by evaporation, and the combinations of temperature and humidity at which core temperature starts rising uncontrollably are well below what was once assumed (Vecellio 2023).

In plain terms: 30C in dry air and 30C in muggy air are different exposures. If your log says your bad days cluster on sticky days rather than simply hot ones, that is consistent with physiology, and it is worth recording humidity alongside temperature rather than temperature alone.

Fluid and salt: what actually changes, and what "drink more water" gets wrong

Sweating costs you water and sodium, and replacing both matters when losses are heavy. Guidance from exercise physiology is that fluid should be replaced at rates close to sweating rate, that dehydration of about 2% of body weight starts to impair function and raise heat injury risk in environments above 30C, and that sodium should be included when losses are large (Coyle 2004). This is why the electrolyte sachets that come up constantly in summer IBS threads are not a fad.

But here is the part the generic advice skips. Losing fluid does reduce stool output, and that has been measured. In a randomised crossover study, eight healthy men spent one week drinking more than 2,500 ml of beverages a day and another week drinking less than 500 ml, with diet and activity standardised. Stool frequency fell from about 6.9 to 4.9 movements a week and stool weight fell from 1.29 kg to 0.94 kg a week during fluid restriction. Transit time did not change. The authors concluded that low fluid intake may be a cause of constipation in some people, and then added the sentence everyone quoting this study leaves out: there is no evidence that increasing fluid intake within feasible limits helps chronic constipation (Klauser 1990).

One thread describes the paradox precisely: someone who is normally IBS-D found themselves constipated and in pain through a heatwave despite drinking constantly (r/ibs thread). That is a coherent picture. Heavy sweat losses with plain water replacement can leave you replacing volume without replacing sodium, and the stool output data show that net fluid deficit reduces what comes out.

The summer plate changes more than anyone admits

This is the suspect with the most evidence and the least glamour, and it is the one worth testing first.

Several things shift on a summer plate at once. Fruit intake goes up, and the fruit that is in season is the fructose and sorbitol-rich end of the range. Cold drinks go up, including sugar-free ones sweetened with polyols. Ice cream goes up. Alcohol goes up. Barbecue food shifts towards fatty meat and onion-heavy salads and dressings. Evening meals get later and bigger.

Fructose and sorbitol are incompletely absorbed in the normal small intestine, and their malabsorption produces abdominal complaints and diarrhoea that are, in the words of one review, indistinguishable from those of functional bowel disease (Fernandez-Banares 2009). This is not an exotic sensitivity. It is ordinary physiology meeting an unusual dose.

NICE's first-line dietary advice for IBS already anticipates this. It suggests limiting fresh fruit to about three 80 g portions a day, spreading them out, reducing fizzy drinks and alcohol, and, specifically for people with diarrhoea, avoiding sorbitol, which it notes turns up in sugar-free sweets, chewing gum, drinks and some slimming products (NICE CG61). Read that list again in June. Sugar-free squash, sugar-free ice lollies, an afternoon of cherries, a bowl of watermelon and a mango smoothie is a very different fermentable load from a winter day, without a single "unhealthy" item in it.

One person in the seasonal thread put it plainly: they eat far more fruit in summer, listing melons, pineapple, three kinds of berries, peaches and plums, where winter is mostly apples (r/ibs thread). Another said simply that summer means more fruit and raw vegetables and that this wrecks them.

If lactose is your question, our guide on why lactose-free milk can still upset your stomach covers what else is in dairy besides the sugar. For the summer drinking side, what the evidence actually says about alcohol and IBS is more nuanced than "alcohol is a trigger". And because these foods rarely arrive one at a time in summer, how FODMAP stacking works across a single day is probably the most useful thing to read before a barbecue weekend.

Worth being clear about what a low FODMAP approach is and is not. A network meta-analysis of 13 randomised trials in 944 patients ranked it first against habitual diet for global symptoms, abdominal pain and bloating, though the authors noted most trials were in specialist care and did not study reintroduction (Black 2022). The ACG guideline recommends a limited trial of it (Lacy 2021). "Limited" is the operative word: it is a short, structured process with a reintroduction phase, ideally run with a dietitian, and it is not a summer-long way of eating.

Summer is gastroenteritis season, and that has a long tail

This is the mechanism with the hardest evidence behind it, and it is the one summer IBS articles almost never mention.

Bacterial gastroenteritis is strongly seasonal, and temperature is part of why. A time-series analysis of Campylobacter reports in England from 1989 to 1999 found a linear relationship between mean weekly temperature and reported cases: each 1C rise corresponded to about a 5% increase in reports, up to a threshold of 14C, with no relationship outside that range. The authors concluded the effect is likely indirect, acting through other pathways rather than temperature itself (Tam 2006). Those pathways are the obvious ones: food left out, barbecues, picnics, longer chains between fridge and plate.

Why that matters for IBS is the tail it leaves. A meta-analysis of 45 studies covering 21,421 people followed after infectious enteritis found pooled IBS prevalence of about 10.1% at 12 months and 14.5% beyond 12 months. Risk of IBS was 4.2 times higher in people who had enteritis in the previous 12 months than in those who had not, and still 2.3 times higher more than a year on. Risk was higher in women, and in people with anxiety, depression, somatisation or antibiotic exposure around the infection (Klem 2017).

Travel compounds it. A meta-analysis of six studies found travellers' diarrhoea associated with a pooled relative risk of 3.35 for post-infectious IBS, with overall incidence of 5.4% in people who had travellers' diarrhoea against 1.4% in those who had not (Schwille-Kiuntke 2015). And where antibiotics and hospital exposure enter the picture, over 20% of patients develop IBS after Clostridioides difficile infection, according to a meta-analysis of 15 studies, though the heterogeneity was very high at 96% and the authors flagged publication bias (Saha 2022).

One person in the seasonal thread mentioned having had a full intestinal infection, and that it always seemed to land at the beginning of summer. That is anecdote, but it sits on top of a real seasonal curve.

Holidays break every routine your gut relies on

Summer is also when the scaffolding comes down. Meal times move. Sleep moves. You eat food cooked by other people, in portions you did not choose, later than usual. You travel, and travel means unfamiliar bathrooms.

One person in the seasonal thread described having a "shy bowel" and being unable to go in an unfamiliar bathroom, which turned every trip into a backlog. Another said their worse summers were specifically the ones with travel in them. That is not a medical mechanism you can cite a trial for, but it is a real confounder and it is the reason a summer pattern in your log might have nothing to do with the thermometer.

If your symptoms wax and wane for reasons that never quite resolve into a trigger, why IBS comes and goes covers the broader fluctuation problem, including why the same food can be fine one week and not the next.

Heat, anxiety and the loop between them

Heat has a documented effect on mental health presentations. A case-crossover study of nearly 3.5 million emergency department visits across 2,775 US counties in warm-season months found that days of extreme heat, defined as the 95th percentile of local warm-season temperature, were associated with an 8% higher rate of visits for any mental health condition, and a 7% higher rate for anxiety, stress-related and somatoform disorders specifically (Nori-Sarma 2022).

An 8% increase in emergency visits is a population-level signal, not a prediction about your Tuesday. But it does mean heat is not psychologically neutral, and IBS is a condition where stress and symptom load are wired together rather than merely correlated.

There is also a simpler loop that people describe directly. One post put it exactly: in the heat their heart rate rises, their body reads that as a stress response, they feel their abdomen swell, and they start looking for the nearest bathroom (r/ibs thread). A raised heart rate in heat is normal cardiovascular physiology, because your heart is moving more blood to your skin. But if you have spent years learning to read your body for early warnings, a racing heart is an alarm, and the anticipation does the rest. For the mechanism behind that loop, our post on whether stress can cause an IBS flare goes through the gut-brain evidence properly.

Sleeping badly in a hot room shows up the next day

Hot nights cost you sleep, and in IBS that has been measured prospectively. Twenty-four women with IBS kept sleep and symptom diaries across a menstrual cycle and wore actigraphs for a week. Poorer self-reported sleep quality significantly predicted higher next-day abdominal pain, anxiety and fatigue. Objectively measured sleep efficiency predicted worse next-day anxiety and fatigue. Reversing the analysis, symptoms did not predict subsequent sleep (Buchanan 2014).

Report that accurately, though. Sleep quality predicted next-day pain, not next-day gastrointestinal symptoms, which did not reach significance in that small study. So the honest claim is that a run of hot, broken nights is a credible reason for a painful week, and a weaker one for a week of diarrhoea.

The grass pollen overlap almost nobody mentions

Here is a genuinely novel summer mechanism with new data behind it. Researchers retrospectively analysed 61 adults with IBS seen between 2021 and 2024, classifying them by allergic sensitisation to grass, house dust mite, or neither, and comparing gastrointestinal symptom scores outside pollen season with scores during it. Mean symptom scores rose significantly during pollination season only in the grass-sensitised patients, and only within the IBS-D subgroup. Neither the house dust mite group nor the unsensitised group changed, and the overall cohort showed no significant variation (Rossi 2025).

Sixty-one patients, retrospective, one centre: this is a small signal, not a settled finding. But it is the only study we found that measured symptom change across a summer season in people who already have IBS, and it suggests that for some people the summer variable is pollen rather than temperature. If your bad summer window tracks grass pollen counts more closely than the thermometer, and you have hay fever, that is a specific thing to raise with your doctor rather than a general one.

Moving more helps, until the heat turns it into heat stress

Summer means more walking, more gardening, more outdoor work. That is mostly good news. In a randomised controlled trial, 102 patients with IBS were assigned either to increase physical activity with physiotherapist guidance or to maintain their lifestyle. The physical activity group improved significantly more on the IBS severity scoring system, with a median change of minus 51 points against minus 5 in controls, and fewer of them deteriorated over the study (Johannesson 2011).

The catch is dose and conditions. Ordinary activity is not the same as exertional heat stress, and the gut damage findings discussed earlier came from hard exercise in hot conditions (Costa 2020, Osborne 2019). Several people in the heat threads describe the same practical solution independently: break the exposure up. One described 30 minutes outside followed by 10 minutes in, repeated, as far more tolerable than three unbroken hours. Another, who works outdoors, eats light through the day and saves the real meal for after a cold shower at home.

Medicines and the heat: a conversation to have before the heatwave

This one came from a Reddit comment, and it turns out to be well founded. Someone warned another poster that an antispasmodic they were both familiar with can reduce your ability to sweat, and that this matters in heat.

The pharmacoepidemiology supports the general principle. A sequence symmetry analysis of 6,700 veterans with a first hospital admission for dehydration or heat-related illness found significantly higher risk following initiation of several common medicine classes, including anticholinergic agents, antidepressants, antipsychotics, NSAIDs and cardiovascular medicines. Risk estimates ranged from 1.17 for SSRIs to 2.79 for an ACE inhibitor plus diuretic combination. Notably, no significant association was found for anticonvulsants, hypnotics, anxiolytics or antihistamines (Kalisch Ellett 2016). This was an observational design in an older veteran population, and it measured admissions after starting a medicine, so it does not translate directly to a 30-year-old on a long-term low dose.

Why it is relevant to IBS specifically: antispasmodics are a first-line option in the NICE guideline, and low-dose tricyclic antidepressants are a recommended second-line treatment for pain in IBS (NICE CG61). Both classes carry anticholinergic effects, and reduced sweating is one of them.

What the seasonal data actually shows

Three datasets exist, and none of them says what the headline suggests.

A community survey. In Sydney, 262 people from a random community sample and hospital staff completed a validated questionnaire. Of the 60 with IBS, 23% reported a moderate or greater seasonal change in bowel symptoms. People with IBS were about three times more likely than people with milder bowel symptoms to report seasonal changes in pain or defecation, and that association was partly explained by somatisation, meaning a general tendency to notice and report physical symptoms (Talley 1995). Note the direction: 23% reported seasonal change, so 77% did not.

Hospital records. A multicentre Korean study used standardised records from eight hospitals covering 2019 to 2023. Seasonal variation in new IBS diagnoses was evident and correlated significantly with temperature and humidity. But the peak was in autumn, with summer second (Hong 2026). And these are new diagnoses, which measure when people present to hospitals, not how existing symptoms change.

Admissions data. In Rome and Valencia across 2001 to 2010, a rise in summer temperature from the 50th to the 75th percentile was associated at short lag with an increase in paediatric gastrointestinal admissions in both cities (Iniguez 2016). Children, hospital admissions, not IBS. It tells you heat and gut presentations move together at a population level, and nothing more.

A worked example: one heatwave week, four suspects

Imagine a week in late July. Five bad days out of seven, mostly loose stools and cramping in the afternoon. The obvious conclusion is heat. Here is what a log would need to separate.

Monday. 31C and humid. Walked 40 minutes to the station in the sun. Breakfast normal. Lunch a shop-bought salad with dressing. Afternoon: two peaches and a sugar-free iced tea. Symptoms at 4pm.

Tuesday. 32C. Worked from home in a cool room. Same breakfast. Melon and berries mid-morning, ice cream after dinner. Symptoms at 9pm.

Wednesday. 29C, dry, breezy. Nothing unusual eaten. No symptoms.

Thursday. 33C. Barbecue at a friend's house: burgers, coleslaw, three beers, watermelon. Bed at 1am, room too hot to sleep. Symptoms overnight and all Friday.

Friday. 33C. Exhausted, slept four hours. Ate almost nothing. Symptoms continued.

Read that log without a theory and heat is not the standout variable, because Wednesday was also hot and was fine. What separates the bad days from the good one is the fruit and polyol load, the alcohol, the late heavy meal, and the ruined night. Heat is the thing that made all of those more likely, which is a different claim from heat acting on your bowel directly.

That is the distinction worth chasing. Heat may be a cause of causes in your summer rather than a cause in itself, and that matters, because the things it causes are the ones you can actually change. You cannot turn the weather down. You can move the fruit to one portion at a time and put the barbecue earlier in the evening.

Working out which variable is doing the work is harder than it looks when four of them move together, which is why finding out what actually triggers your IBS is built around testing one thing at a time rather than eliminating everything at once. Logging quickly enough to capture a real week is the practical obstacle, and it is the reason Clairop lets you describe a meal out loud rather than typing it in.

What tends to help, ranked honestly by evidence

Good evidence, in IBS generally:

• Regular meals, not skipping, not leaving long gaps, per NICE first-line advice (NICE CG61).
• Limiting fresh fruit to about three portions a day, spread out, and avoiding sorbitol if you have diarrhoea (NICE CG61).
• Keeping activity up, since increased physical activity improved IBS severity scores in a randomised trial (Johannesson 2011).
• A short, structured low FODMAP trial with dietetic support if first-line advice has not worked (Black 2022, Lacy 2021).

Good evidence for heat, not tested in IBS:

• Replacing fluid at something like the rate you are losing it, and including sodium when losses are heavy or prolonged (Coyle 2004).
• Breaking up heat exposure rather than enduring it continuously, which follows from the dose-dependence of heat strain (Vecellio 2023).
• Food hygiene discipline at barbecues and picnics, given the temperature dependence of Campylobacter reports (Tam 2006).

Widely recommended, thin or absent evidence:

• Ice-cold drinks as a gut treatment. Drink temperature does not appear to change gastric emptying or intestinal absorption, though ice slurry is effective for lowering core temperature (Tan 2015). Cold drinks are pleasant and they help you cool. Nobody has shown they settle an IBS gut.
• Drinking far beyond your usual intake to relieve constipation, which the study everyone cites explicitly does not support (Klauser 1990).

When summer symptoms are not IBS at all

Some summer gut symptoms are heat illness, and heat illness is a medical emergency at the severe end. In a case series of 26 critically ill patients admitted with heat-related illness during an Indian summer, gastrointestinal symptoms were present in 30%, alongside universal neurological involvement, and mortality was 34% (Kalaiselvan 2015). That is an intensive care population, deliberately at the extreme end, and it is here to make one point: nausea and vomiting in severe heat can be a sign of something other than your usual condition.

Get out of the heat, cool down and seek medical help promptly if gut symptoms in hot weather come with confusion, a very high temperature, stopping sweating, fainting, severe headache, or muscle cramps with dark urine.

There is a second pattern worth naming. If your summer problem is dizziness and a racing heart on standing as much as it is your bowel, and it has been going on for years, that combination deserves a proper assessment. Gastrointestinal symptoms are common in postural orthostatic tachycardia syndrome, which is a cardiovascular autonomic disorder affecting mostly younger people with a strong female predominance, and where heat tolerance is typically poor (Fedorowski 2019, Tu 2020). That is a reason to ask a doctor a question, not a diagnosis to make from a blog post, and the overlap between the two conditions is genuinely complicated.

And if the pattern is diarrhoea, bloating and weight change that does not track the weather at all, it is worth ruling out the look-alikes. Our comparison of SIBO and IBS symptoms goes through where the overlap is and where the testing is contested.

Myths about IBS and hot weather

"Heat speeds up your digestion, that is why you get diarrhoea." No study we could find has measured transit time in people with IBS across ambient temperatures. The documented direction of the heat response is blood moving away from the gut, not a straightforward speeding up (Gravel 2021).

"It is the barometric pressure." This comes up constantly in the threads, often confidently, sometimes with claims about serotonin attached. We could not find studies testing barometric pressure against IBS symptoms. Rain and pressure swings may well matter for some people, but nobody has shown it and no one should assert it.

"An ice-cold drink shocks your gut." Drink temperature does not appear to meaningfully change gastric emptying or intestinal absorption (Tan 2015). If cold drinks upset you, the more likely culprits are what is dissolved in them: fructose, sorbitol, carbonation or caffeine.

"Just drink more water and you will be fine." Replacing losses is worth doing. It will not touch a fermentable sugar load, a gut infection, a broken sleep pattern or a 1am barbecue, and the constipation study most often used to justify it says extra fluid does not fix chronic constipation (Klauser 1990).

"Everyone with IBS is worse in summer." Plainly not. Every thread on this includes people whose worst season is winter, and one survey put the proportion reporting any meaningful seasonal change at 23% (Talley 1995).

"If it is seasonal it must be psychological." The Talley survey did find seasonal symptom change partly explained by somatisation, and that finding gets misused. Somatisation means a tendency to notice and report physical symptoms; it does not mean symptoms are imagined, and it does not explain the dietary, infectious and sleep changes that also arrive with summer.

If you have Crohn's disease or ulcerative colitis

Most of this page is about IBS, where there is no inflammation to worry about. With IBD the calculation is different in two ways.

First, dehydration is a larger risk, particularly with an ileostomy or extensive small bowel disease, where sodium and fluid losses are higher to begin with and a hot week can tip a precarious balance. That is worth a specific conversation with your IBD team before a heatwave or a hot holiday rather than after.

Second, and more importantly, do not attribute new or worsening symptoms to the weather. Increasing stool frequency, bleeding, urgency or pain during a summer are reasons to contact your IBD team and, where appropriate, check inflammation objectively, not reasons to wait for autumn. How to tell the difference is covered properly in how to know if your ulcerative colitis is flaring and how to tell if you are in a Crohn's flare.

When to see a doctor

See a doctor promptly if any of these appear, in any season:

• Blood in your stool, or black tarry stools
• Unexplained weight loss
• Fever alongside gut symptoms
• Symptoms that wake you at night
• Symptoms starting for the first time after the age of 50
• A family history of bowel cancer, coeliac disease or IBD
• Anaemia, or feeling increasingly breathless and tired

Also worth a routine appointment: a summer pattern that has been getting worse year on year, a summer in which your symptoms changed character rather than intensity, or gut symptoms that started after a holiday stomach upset and never fully went away. That last one is the post-infectious picture, and it changes how a clinician approaches your case (Klem 2017).

If you want to take something concrete to that appointment rather than a general impression that summers are bad, the useful artifact is a log that captures a hot stretch and a mild one, with what you ate, how you slept, and what the weather was doing. Clairop was built to make that kind of record quick enough to actually keep, and to turn it into a summary you can hand over. Our page on how it works explains what it does and does not do.

The honest bottom line

Summer is a confound, not a cause. The heat is real, the physiology that moves blood away from your gut is real, and the thermal hypersensitivity finding suggests a large minority of people with IBS genuinely feel heat more sharply than other people do. But none of that has been tested against IBS symptoms, and the things that have solid evidence behind them are the things summer changes around you: the fruit and polyols on your plate, the alcohol, the late heavy meals, the broken sleep, the travel, and the seasonal rise in gut infections.

That is better news than it sounds. You cannot do anything about a heatwave. You can do something about four of the six.