A fever is a body temperature of 100.4°F (38°C) or higher when measured rectally. This temperature increase is often a beneficial response, indicating the immune system is actively fighting an infection or illness. Most fevers are harmless and resolve on their own. Deciding when a child’s fever requires a call to the pediatrician or an emergency visit depends on the child’s age, the temperature reading, and the presence of other concerning symptoms.
Methods for Accurate Temperature Measurement
Obtaining a precise temperature reading is the first step in deciding on the appropriate course of action, and the most reliable method changes depending on the child’s age. For infants younger than three months old, the rectal method is considered the gold standard because it provides the closest estimate of the body’s core temperature. Digital thermometers used rectally should be lubricated and inserted gently.
As a child grows older, other methods become viable. For children between three months and four years, a rectal temperature is still the most accurate, but a temporal artery (forehead) or a tympanic (ear) thermometer can also be used for screening. Note that ear thermometers are not accurate before six months of age. Oral temperature measurement is reserved for children aged four and older who can reliably hold the thermometer under their tongue. Axillary, or underarm, temperatures are the least accurate method and should be confirmed with a more reliable technique if the reading indicates a fever.
Age-Specific Temperature Thresholds for Contact
The urgency of a fever is directly linked to the child’s age, as very young infants have less developed immune systems and can become seriously ill quickly. For newborns and infants from birth to three months of age, any temperature reading of 100.4°F (38°C) or higher, taken rectally, requires immediate medical attention. This threshold is absolute and should prompt a call to the pediatrician or a visit to the emergency department without delay.
For infants between three and six months old, the guidance is slightly different, though still cautious. A temperature of 102.2°F (39°C) or higher generally warrants a call to the doctor, especially if the temperature does not decrease after administering a fever-reducing medication. Even a lower-grade fever in this age group should be discussed with a healthcare provider if it lasts for more than 24 hours.
For older children, typically those six months and up, the focus shifts away from the exact number on the thermometer, unless it reaches a significantly high level. A fever of 104°F (40°C) or higher should always be addressed by a healthcare provider. Furthermore, any fever that persists for more than 72 hours, or three full days, should be evaluated by a pediatrician, even if the temperature remains low-grade.
Accompanying Red Flag Symptoms
Certain qualitative symptoms indicate a severe illness that requires immediate medical care, regardless of the child’s temperature. These red flags demand immediate evaluation:
- A non-blanching rash (one that does not fade when pressed with a glass).
- A stiff neck, severe headache, or unusual sensitivity to bright light.
- Significant change in responsiveness, such as severe lethargy or difficulty waking up.
- Difficulty breathing, such as rapid or labored breathing that does not improve after clearing the nose.
- Signs of severe dehydration (no wet diapers for several hours, sunken eyes, or lack of tears).
- Any seizure activity, especially if it is the child’s first time experiencing one.
Supportive Home Management and Monitoring
For a mild fever that does not meet the criteria for contacting a doctor, supportive care at home is the best approach to keep the child comfortable. Encourage the child to take in plenty of fluids to prevent dehydration. Water, diluted juice, popsicles, or oral rehydration solutions are excellent choices to help replenish lost liquids.
Comfort measures like dressing the child in lightweight clothing and keeping the room at a moderate temperature can help regulate the body’s heat. A lukewarm bath or cool washcloth applied to the forehead may also offer relief, but cold baths or ice packs should be avoided as they can cause shivering and raise the body temperature.
Fever-reducing medications, such as acetaminophen or ibuprofen, can be used to improve comfort. Parents should consult their pediatrician for the correct dosage and should never give aspirin to children due to the risk of Reye’s syndrome. Medication is not necessary to hit a specific temperature target, but rather to alleviate discomfort and support rest.