Can Hot Weather Trigger Diarrhoea?

Yet another heatwave could be set to hit the south of England before the summer is over.

According to a long range forecast from the Met Office, between 31 August and 14 September, temperatures are likely to be “above average” with a chance that “late season hot spells or heatwaves develop, especially in the south”.

For those who’ve spent weeks struggling to sleep in the stuffy heat, this will undoubtedly elicit a few groans.

You might’ve noticed more headaches or migraines throughout the hotter periods – and some people have even experienced looser stools and diarrhoea as a result of the soaring temperatures.

One person shared on Reddit’s r/UKWeather thread that as soon as the weather gets above 33C they get diarrhoea. “It’s like my body panics and just wants to evacuate everything,” they added.

They’re not alone. “Omg I’ve had that too,” said another commenter. “Multiple times since it’s been hot I’ve had painful and horrific guts, bouts of diarrhoea followed by days of loose stools and nausea.”

While there’s also been a salmonella outbreak to contend with in the UK, which can cause diarrhoea; and travellers returning from Mexico have seen a spike in cyclospora infections (which, again, causes diarrhoea); there are other reasons why the hot weather can trigger a change in bowel movements.

Dr Nikki Ramskill, a GP verified on the healthcare review platform Doctify and founder of The Female Health Doctor Clinic, explained that extreme heat puts the body under physiological stress.

“When we’re trying to cool ourselves down, blood flow is redirected towards the skin and we sweat more, losing both water and electrolytes,” she told HuffPost UK.

“For some people, that combination of heat stress, dehydration and changes in circulation can upset the digestive system and contribute to nausea, abdominal discomfort or changes in bowel habit.”

Routines also change pretty dramatically when it’s hot – we might drink more caffeine, iced drinks or alcohol, and eat more fruit, salads, ice cream or barbecue food. “Some people also reach for sugar-free drinks or foods containing sweeteners such as sorbitol, which can have a laxative effect in larger quantities,” added Dr Ramskill.

Amid record-breaking heatwaves, July also saw a Salmonella outbreak – potentially linked to imported eggs – impact hundreds of people in the UK. Dr Ramskill notes food poisoning is another important factor in why people might experience a dodgy stomach when it’s hot.

“Bacteria multiply much more readily when food isn’t kept at the correct temperature, so barbecues, picnics and food sitting outside for longer than usual can increase our exposure to bugs that cause diarrhoea,” the expert said.

“Foods such as meat, poultry, dairy products and prepared salads need particular care in hot weather.”

So, heat may actually be part of a bigger picture rather than the sole cause.

• Stay hydrated. “Rather than suddenly drinking huge quantities of water, drink regularly throughout the day,” said the doctor. “If you’re sweating heavily or you’ve developed diarrhoea, you’re losing salts as well as water, so an oral rehydration solution can sometimes be useful.”
• Consider food hygiene. “Keep chilled food properly refrigerated, don’t leave food sitting out in the heat, make sure meat is cooked thoroughly and be careful about cross-contamination between raw and cooked foods,” said Dr Ramskill.
• Think about diet. If you’re consuming more caffeine, alcohol, fruit juice, fizzy drinks or products containing artificial sweeteners, consider cutting down to reduce the risk of loose stools.

If you do end up suffering with diarrhoea, the GP advises to concentrate on replacing fluids and eat when you feel able.

“You don’t need to starve yourself, but simple foods may feel easier to tolerate initially. And don’t assume persistent diarrhoea is ‘just the heat’,” she added.

“Most episodes of diarrhoea settle within a few days, but watery diarrhoea can also be caused by infection, medication or an underlying gastrointestinal problem.”

If you have blood in your stool, significant or worsening abdominal pain, an inability to keep fluids down, or signs of dehydration such as dizziness, very dark urine or passing much less urine than usual, seek medical advice.

“Babies, older people and people with certain health conditions can become dehydrated much more quickly, so we need to be particularly careful with them during a heatwave,” ended the GP.