A fever is a temporary rise in the body’s temperature, typically occurring as a response to an illness or infection. This temperature increase is a beneficial biological process, signaling that the immune system is actively fighting off foreign invaders like viruses or bacteria. The body’s internal thermostat temporarily resets to a higher point, creating an environment less hospitable to pathogens. Understanding this protective function is the first step toward managing a fever with confidence. This guide provides actionable, age-specific information to help you determine when a fever requires medical intervention and how to manage it safely at home.
Understanding Fever Thresholds by Age
A precise temperature reading is the starting point for any decision regarding a child’s fever. The most reliable method varies by age: rectal temperature is considered the most accurate for infants up to three months old. Children older than four or five years can usually hold a digital thermometer under the tongue for an accurate oral reading. For children between these ages, temporal artery (forehead) or axillary (underarm) temperatures are often used, though underarm readings are generally the least accurate.
The temperature that constitutes a medical concern changes significantly with the child’s age. For any infant under three months old, a rectal temperature of 100.4°F (38°C) or higher requires immediate medical attention, even if the baby appears well. This strict threshold exists because young infants may not show other clear symptoms of a serious infection. For babies between three and six months old, a rectal temperature exceeding 102°F (38.9°C) warrants a call to the pediatrician for guidance.
As children grow older, their immune systems mature. For children older than six months, a temperature of 103°F (39.4°C) or higher is often the point at which medical advice is sought. Pediatric professionals consider a temperature of 104°F (40°C) or higher to be a high fever that should be treated and monitored closely. The child’s overall appearance and behavior become increasingly important in assessing the severity of the illness compared to the number on the thermometer.
Recognizing When Treatment is Necessary
The mere presence of a fever, especially a low-grade one between 100°F and 102°F, does not automatically necessitate treatment. A fever is not inherently harmful, and treating it will not make the underlying infection resolve any faster. The primary goal of using fever-reducing medication is to improve the child’s comfort and well-being. If a child has a temperature below 102°F (38.9°C) but is still playful, drinking fluids, and sleeping normally, medication may not be needed.
Treatment becomes necessary when the fever causes noticeable discomfort, such as body aches, chills, or irritability that interferes with sleep, eating, or drinking. For temperatures exceeding 102°F (38.9°C), or for any temperature that is making the child miserable, intervention is appropriate. Children with certain chronic medical conditions, such as heart or lung disease, may require fever treatment at a lower threshold because the elevated temperature can place added stress on their systems.
The duration of the fever is another important factor in deciding when to seek professional advice. If a fever lasts for more than 24 hours in a child under two years old, or more than 72 hours (three days) in a child over two, a call to the doctor is warranted. A persistent fever suggests the underlying illness may require further evaluation, even if the temperature responds to medication. Focusing on how the child looks and acts when the fever is down is often a more reliable indicator of illness severity than the peak temperature itself.
Non-Temperature Warning Signs
While the fever number is a factor, a child’s behavior and physical symptoms are often telling indicators of a serious illness. Parents should look for signs of severe lethargy, such as difficulty waking the child or an inability to rouse them fully. A child who is extremely irritable, inconsolably crying, or whose cry sounds unusual needs immediate medical evaluation. Any change in consciousness or a glassy-eyed appearance suggests the need for urgent care.
Signs of dehydration are a high-priority warning sign, regardless of the fever’s height. These include significantly reduced urination, such as no wet diapers for six to eight hours in infants, or not urinating for that time in older children. Other symptoms are a dry mouth and tongue, a lack of tears when crying, and sunken eyes. If an infant’s soft spot (fontanelle) appears sunken, this is a clear sign of fluid loss.
Specific physical symptoms combined with a fever signal a potential medical emergency. A stiff neck, severe headache, or sensitivity to bright light should prompt an immediate medical visit. A rash that does not fade or blanch when pressed with a glass can indicate a serious bacterial infection and requires emergency care. Difficulty breathing, such as rapid or labored breaths, or a bluish tint to the lips or nails, should also be treated as an emergency. Febrile seizures, which are convulsions triggered by a rapid rise in temperature, are common and usually harmless, but the child should still be checked by a doctor after the first occurrence.
Safe and Effective Fever Management Strategies
Once the decision is made to treat a fever for comfort, utilizing the correct medication and dosage is paramount for safe management. Acetaminophen (Tylenol) is approved for infants over two months of age, while ibuprofen (Advil or Motrin) is approved for infants over six months. The most important rule is to dose by the child’s current weight, not their age, and to use the measuring device that comes with the medicine to ensure accuracy. Never use a kitchen spoon for measuring liquid medication, as this can lead to an incorrect dose.
Parents should strictly avoid giving aspirin to any child or teenager due to the risk of Reye’s syndrome, a rare but serious condition affecting the liver and brain. While alternating between acetaminophen and ibuprofen is common, this practice can increase the risk of accidental overdose and should only be done under the explicit direction of a healthcare provider. Acetaminophen can be given every four to six hours, with a maximum of five doses in a 24-hour period, while ibuprofen is typically given every six to eight hours.
Beyond medication, supportive care focuses on hydration and comfort. Offering plenty of fluids, such as water, electrolyte solutions, or breast milk, is essential to prevent dehydration. The child should be dressed lightly to allow heat to escape, and the room temperature kept comfortable. Sponging the child with lukewarm water can help bring down a very high fever, but only after medication has been given. Sponging should be stopped immediately if the child shivers. Never use cold water or rubbing alcohol for sponging, as this can be harmful.