August 2025

Babies are especially vulnerable during hot days and heat waves. But is that because their temperature regulation system is not yet "finished," or something else?

In a narrative review within the GoHot Project, Eline van de Kamp and Hein Daanen examined what is known in science about how babies regulate their body temperature in warm conditions. They look at studies on babies themselves and explain what unique characteristics influence heat balance in babies.

Key findings:

• Babies have a larger surface area of skin relative to their weight than adults. This can help them lose heat in moderate temperatures, but actually works against them when it is warmer outside than their skin. In extreme heat, babies therefore absorb heat from their surroundings faster.

• Humans' relative heat production peaks around 8-9 months of age, so relatively large amounts of heat must be dissipated during this stage of life.

• To cool down, the body sends extra amounts of blood to the surface of the skin so that more heat can be released to the environment. Possibly in babies, an even greater portion of the blood volume goes to the skin during heat, leaving less blood for blood flow to other organs and may cause symptoms such as headaches or fatigue more quickly.

• Babies can sweat from birth. However, they do produce less sweat per sweat gland. It is still unclear whether this is because the sweat glands are not yet fully developed, or whether it is, for example, a protective mechanism to combat moisture loss and dehydration.

The researchers conclude that babies' vulnerability arises primarily from the combination of their unique body characteristics and the fact that they are completely dependent on caregivers. Importantly, very little research has been done with babies themselves. Exactly how they respond to different types of heat, we do not yet know. In the continuation of the GoHot project, we will try to get answers to this.

For now, it is important for people to be aware of the increased risk babies face during hot days. Make sure babies stay in the shade as much as possible, drink plenty of fluids, are not overdressed, and pay close attention to signs of overheating.

Read the full article here.