New parents often notice their baby’s head feels warm while their cheeks, hands, or feet feel cool. While concerning, this temperature disparity is usually a normal reflection of the infant’s still-developing biological systems. Understanding the reasons behind this difference, and knowing how to accurately assess your baby’s core temperature, is important.
Why Temperature Differences Are Normal in Infants
An infant’s thermoregulation system, the body’s method for controlling internal temperature, is still immature compared to that of an adult. Babies are not yet efficient at adjusting their temperature, which leads to quicker changes on the surface of their skin. Their body surface area is significantly larger relative to their body weight, meaning they can lose or gain heat much faster, especially through exposed areas.
The head plays a disproportionately large role in an infant’s temperature regulation. Since a substantial amount of blood circulates close to the surface of the scalp, heat is readily lost or retained in this area, making the head feel noticeably warm.
When the body works to maintain warmth in the core, it constricts blood vessels in the extremities, a process called vasoconstriction. This mechanism diverts warm blood away from the cooler extremities, such as the hands, feet, and cheeks, to safeguard the internal organs. Consequently, the skin temperature you feel on the cheeks or limbs is superficial, fluctuating easily based on ambient air, and may be much lower than the actual stable core temperature.
Environmental factors or activity can also cause temperature differences. Overdressing an infant traps heat near the skin, and a warm room can cause the head to feel hot since heat is lost from this large exposed surface. Conversely, exposure to cool air makes the cheeks feel cold as the body conserves heat internally.
How to Accurately Check Your Baby’s Temperature
Because touch is unreliable for determining core temperature, parents should use a digital thermometer to get an objective reading. The method considered the gold standard for accuracy in infants under three months of age is a rectal temperature. For this, a lubricated digital thermometer is inserted gently about half an inch to one inch into the rectum.
For older infants, or as a preliminary screening tool, other methods may be used, though they are often less accurate. Temporal artery thermometers, which scan the forehead, are convenient but can provide misleading results if the baby is sweating or if the device is used in a cold environment. Axillary (armpit) temperatures are also an option but tend to be the least reliable, often reading a full degree lower than the core temperature.
A fever in infants is defined as 100.4°F (38°C) or higher when taken rectally or temporally. If using an armpit reading, 99°F (37.2°C) or higher is considered elevated. Always follow the manufacturer’s instructions for the specific device you are using, as readings can vary based on the site of measurement.
When to Seek Medical Attention
The physical feeling of a warm head and cool cheeks, without accompanying symptoms, is rarely a cause for concern. Medical attention is necessary when the baby’s behavior or a measured core temperature suggests illness. Any rectal temperature of 100.4°F (38°C) or higher in an infant under three months old requires an immediate call to a healthcare provider.
Beyond a specific temperature reading, parents should focus on the baby’s overall clinical picture. Signs of serious illness include unusual lethargy, where the baby is difficult to wake or is noticeably less active than normal. Extreme irritability, where the baby cries inconsolably, also warrants professional advice.
It is also important to monitor for signs of dehydration, which can sometimes accompany a temperature fluctuation. Refusal to feed or difficulty breathing are serious symptoms. Prompt medical evaluation is necessary, regardless of the temperature difference felt on the skin, if you observe:
- A sunken soft spot (fontanelle) on the top of the head.
- A significant decrease in the number of wet diapers.
- Refusal to feed.
- Difficulty breathing, such as rapid or labored breaths.