High temperatures don't just cause intense fatigue. They can also disrupt your digestive system, leading to diarrhea, stomach aches, or bloating. These issues further weaken your body, which is already susceptible to dehydration during a heatwave. In this article, we explain the link between heat and diarrhea, and we give you simple tips to reduce risks and react effectively.
Heatstroke, sunstroke, fluid deficit: what are we talking about?
What is heatstroke?
Heatstroke occurs when your body temperature exceeds 40°C and your natural regulatory mechanisms are no longer sufficient to cool you down. Unlike sunstroke, which is linked to direct sun exposure, you can be affected even in the shade.
If you experience signs such as red and dry skin, confusion, loss of consciousness, or convulsions, go to the emergency room quickly for appropriate treatment, as your life may be at risk.
How do you know if you have sunstroke?
Sunstroke corresponds to an overheating of the body caused by prolonged sun exposure or intense physical activity. It manifests as headaches, nausea, extreme fatigue, fever, and sometimes diarrhea. Although it is generally less severe than hyperthermia, it can lead to complications if treatment is not sought in time.
Good reflexes: at the first symptoms, get into the shade, hydrate yourself, and cool your body with a damp towel, a lukewarm shower, or ventilation.
What is dehydration?
Dehydration occurs when you lose more fluids and minerals than you absorb, particularly through sweat, diarrhea, or vomiting. During a heatwave, this risk is amplified. It can be both a consequence of hyperthermia or sunstroke and an aggravating factor, as it disrupts intestinal function.
Who is most at risk?
- Infants and young children.
- Elderly people, who feel less thirsty and regulate their fluid loss less effectively.
- Athletes, due to massive fluid loss through perspiration.
- Patients taking diuretics, laxatives, or certain antibiotics.
Why do we get diarrhea in summer?
In summer, food left at room temperature or poorly stored quickly becomes a breeding ground for bacteria like Salmonella or Escherichia coli. The risk of gastroenteritis then increases sharply.
When traveling abroad, you may also develop " traveler's diarrhea ". According to Vidal, "this infectious disease affects between 25 and 60% of people in tropical or subtropical areas." The causes are multiple: food contamination, parasites, viruses, or consumption of unsafe water.
The direct impact of heat on your intestines
When the outside temperature rises, your body tries to cool down. To do this, it dilates blood vessels and directs blood flow to the skin. The digestive system then receives less oxygen, which slows its ability to digest and absorb nutrients properly.
Furthermore, heat stress can alter the balance of the intestinal microbiota, i.e., the bacteria that aid in your digestion, and cause reactions such as bloating and looser or liquid stools. These effects are often more pronounced if you already suffer from a chronic digestive disorder, such as irritable bowel syndrome or certain inflammatory diseases.
The vicious cycle of heatwave – diarrhea – dehydration
During hyperthermia, inflammation disrupts your digestive system. Fluid loss reduces nutrient absorption, promotes frequent bowel movements, and accentuates intestinal fragility.
A real vicious cycle sets in:
- Heatstroke and sunstroke cause fluid and mineral loss.
- Fluid deficit worsens digestive problems, including diarrhea.
- The latter leads to even more losses.
How to prevent and treat these disorders in summer?
Prevent sunstroke and dehydration
Adopt a few simple habits:
- Avoid the sun between 10 a.m. and 4 p.m.
- Wear a hat and light clothing.
- Drink regularly in small sips, even if you're not thirsty.
- If necessary, use oral rehydration solutions (ORS).
- Consume fresh food, well-washed and stored cold.
- Limit intense physical exertion.
You can also use Hydratis tablets to compensate for mineral loss.
How to treat heat-related diarrhea?
Prioritize oral rehydration with water, broths, or an ORS-type solution. Rest your digestive system by consuming easily digestible foods, such as bananas, rice, or applesauce. Avoid fatty, spicy dishes, as well as alcohol and coffee.
Consult a doctor quickly if symptoms persist for more than 48 hours, if you observe blood in your stool, or if fever increases.
The right actions in case of heatstroke
Immediately cool the person down with a lukewarm shower or damp towels, place them in a cool area, and have them drink in small sips. If you are outside, air-conditioned shops will be your best allies.
If their condition worsens, contact emergency services immediately.
During periods of intense heat, maintaining good hydration is essential to support the normal functioning of your body and to compensate for water and mineral losses linked to perspiration or digestive disorders. Hydratis electrolyte tablets, rich in electrolytes, can help you optimize your daily rehydration, especially in cases of diarrhea, prolonged heat exposure, or intense physical activity. Easy to transport and use, they are a practical solution to maintain your fluid balance throughout the summer.
Conclusion: better understanding the effects of heat to protect your digestive health
In summer, heat and diarrhea form a formidable duo that can put your health to the test! To limit complications, adopt the right preventive measures and react quickly at the first symptoms.
Remember: the duration of a diarrheal episode can vary from a few hours to several days, depending on your history and general condition. If in doubt, do not hesitate to consult a healthcare professional, whether for yourself, your child, or any vulnerable person. You will always find reliable information from your doctor or pharmacist.
Bibliography
Asmara, I. G. Y. (2020). Diagnosis and management of heatstroke. Acta Medica Indonesiana, 52(1), 90–97. https://pubmed.ncbi.nlm.nih.gov/32291378/
VIDAL. (2024, July 10). Traveler's diarrhea or Turista. VIDAL. https://www.vidal.fr/sante/voyage/maladies-voyage/diarrhee-turista.html
Gisolfi, C. V. (1993). Effects of exercise and heat on gastrointestinal function. In B. M. Marriott (Ed.), Nutritional needs in hot environments: Applications for military personnel in field operations (pp. 103–120). Washington, DC: National Academies Press. https://doi.org/10.17226/2094
Gotfried, J. (2025, May). General review of gastroenteritis. MSD Manuals.
en/en/
