By Dr. Maria Chiara Matteucci, Specialist in Nephrology and Pediatrics at Aventino Medical Group, Rome
Heat doesn’t affect everyone the same way: why children are more at risk
Summer brings bright days and time outdoors, but for children, sun exposure and excess heat can pose an underestimated risk—even to their kidneys. Their bodies are not yet able to regulate temperature effectively and have a higher water requirement compared to adults.
Body temperature is maintained by balancing heat generated through metabolism and the heat absorbed from the external environment.
Evaporation is the main mechanism for losing body heat in a hot environment, but it can be inefficient when humidity levels are high.
In addition to temperature and humidity, the higher risk of heat-related illness in children is linked to specific age-related characteristics.
Compared to adults, children have a higher basal metabolic rate, which leads to greater heat production per kilogram of body weight.
In younger children, excessive heat exposure can quickly lead to dehydration and kidney stress—even without visible symptoms. A larger body surface area in relation to body weight results in increased heat absorption from the environment, and their sweat response is still immature, making them more vulnerable.
The risks increase in newborns, very active children, and in cases of prolonged exposure. Effective protection and awareness of these risks are not just good habits—they are essential clinical prevention measures.
The chart shows the relationship between temperature and relative humidity and the risk of heat stroke. The closer you get to the red zones, the higher the risk.
Dehydration and kidney stress: a little-known link
When it’s hot, the body loses fluids and essential minerals. If these are not replenished, the kidneys—responsible for filtering the blood and regulating salts—can become strained.
In children, even a moderate loss of fluids can reduce circulating blood volume, lowering the supply of oxygen and nutrients to the kidneys. This may cause a temporary decline in kidney function, and in more severe cases, lead to acute kidney failure.
What are the warning signs of this risk? Very concentrated or reduced urine output, unusual tiredness, unexplained fever, irritability.
It’s crucial to recognize these symptoms early and respond with adequate hydration and, if necessary, a specialist evaluation.
Heat and children: which signs to watch for
In children, heat stress can begin subtly but progress quickly. Some of the most common signs include:
- Persistent thirst
- Dry mouth
- Sleepiness or irritability
- Fever
- Dark, reduced urine
- Muscle cramps or nausea
Recognizing these symptoms early and responding with good hydration and, if needed, specialist care is essential.
In infants, a sunken fontanelle may also indicate dehydration.
Since children often struggle to express discomfort, adults must stay alert.
If a child seems unusually unresponsive or complains of vague discomfort after sun exposure, heat stress should be suspected.
The 5 golden rules for preventing heat stress
Proper protection allows children to enjoy summer safely. Here’s what to do:
- Offer water frequently, even if they don’t ask for it
- Avoid the hottest hours, between 11:00 a.m. and 5:00 p.m.
- Use hats and light clothing, preferably in light cotton
- Apply high sun protection (SPF 50+) every two hours
- Encourage shaded activities with regular breaks, especially during sports
- Consider any conditions and/or medications that may reduce sweating
These simple precautions are also recommended by the Italian Society of Pediatrics and can prevent up to 90% of heat-related dehydration cases.
When should you consult a specialist?
Some signs require particular attention, especially if they persist for more than 24–48 hours:
- Persistent fever not linked to an evident infection
- Pronounced tiredness or lethargy
- Scant or unusually concentrated urine
- General malaise or nausea
In these cases, it is helpful to consult a pediatric nephrologist to rule out possible kidney involvement.
What does the specialist assess?
A specialist consultation may include:
- Urine tests, to detect traces of blood, proteins, or signs of dehydration
- Blood tests, to monitor creatinine, urea, and electrolyte levels (sodium, potassium)
- Clinical assessment, to identify any predisposing risk factors (urinary anomalies, family history, recurrent infections)
Early detection of kidney imbalance allows for targeted intervention and helps prevent complications—especially during the hottest months.
Conclusion
Kidney health begins with small signs
In summer, even mild discomfort may indicate excessive strain on young, still-developing kidneys.
Paying attention to symptoms and acting quickly means protecting children today and preventing future issues.
Kidney health begins with small signs
Timely checkups can make a difference.
Listen to your body’s signals—trust those who know how to read them!
Pediatric Nephrology – Aventino Medical Group
