Fever in Babies and Children – Thermometers, Readings, Causes

The normal human body temperature is often cited to be about 37 °C (or 98.6 °F). However, temperature readings from different regions of the body differ from each other. Still the variation in body temperature measurements is within a small range. For children, the normal body temperature ranges from 36.5 °C (or 97.7 °F) to 37.5 °C (or 99.5 °F). During the course of a day, the body temperature of a child can change by as much as 0.5 °C (or 1-1.5 °F).

Fever in Children and Newborns

Fever refers to an abnormal rise in the core body temperature above the normal range. Depending on the extent of rise in core body temperature, fever can be classified as low-grade and high-grade fever.

Low-Grade Fever

In children, a core body temperature between 37.6 °C and 38 °C is considered to be low-grade fever. This can be treated with simple over-the-counter antipyretic medicines. But medicines are not always necessary. A low-grade fever may go away on its own.

Moderate to High Fever

A core body temperature that is above 38 °C (or 100.4 °F) but less than 40 °C (or 100.4 °F) is considered to be mild or moderate fever. This type of fever can also be managed with antipyretic medication in a home setting. However, medical attention should be sought in case of any worry. When the core body temperature rises above 40 °C (or 104 °F), the fever is classified as a high-grade fever that needs to be treated as a medical emergency.

Newborn Baby Fever

In case of newborns, even a fever with a core body temperature above 38.3 °C (or 101 °F) should be treated as a medical emergency. In fact, it is better to treat any temperature above 38.3 °C (or 101 °F) as a medical emergency in infants up to the age of 3 months.

Fever Diseases

Febrile illnesses (or diseases characterized by fever) in children can cause fluctuation of core body temperature by up to 1 °C within a period of 24 hours. But these fluctuations do not indicate the changes in the underlying condition accurately. When the core body temperature rises above 38.9 °C (or 102 °F) in children, febrile seizures may occur. In most cases, febrile seizures are not harmful but can be very distressing for both the parents as well as the child.

Therefore, one should monitor the body temperature carefully in feverish children and try to avoid febrile seizures by controlling the rise in temperature. In newborn babies, fever is a cause of great concern. This is because the immune system of a baby is not developed enough to fend off infections. Babies with fever become irritable, demand attention, and have a restless sleep. This typically translates into sleepless nights for the parents and caregivers.

Read more on persistent fever of unknown origin.

Measuring Body Temperature in Children

A variety of thermometers are now available for measuring body temperature in children. These include glass thermometers, ear thermometers, fever strip thermometers and digital mouth thermometers. Glass thermometers can be used in most cases to measure body temperature accurately. A glass thermometer can be used to measure body temperature orally, rectally, or in the armpit.

In children (especially in infants who are less than 3 months old), measurement of rectal temperature is the most accurate way to determine core body temperature. Oral temperature measurements are usually slightly lower than the rectal temperature measurements. In recent times, ear thermometers have gained widespread popularity, especially for checking body temperature in children.

These ear thermometers are not uncomfortable and provide a quick and convenient mode of assessing body temperature. However, a high temperature readout from an ear thermometer should be cross checked by using an oral thermometer. Digital mouth thermometers have also become popular now. However, a high temperature readout using a digital mouth thermometer should also be cross checked by repeating the measurement with a glass thermometer.

Fever strip thermometers are typically placed on the forehead to measure the body temperature. However, readings from these are not very reliable. In case of a high temperature readout, a glass thermometer should be used to confirm the findings. Depending on the brand of manufacturer, temperature readings from digital, ear and fever strip thermometers exhibit significant variations.

Therefore, these methods should not be relied upon when close monitoring of body temperature is required in case of high fever in children.

Causes of Fever in Babies and Children

It is important to identify the cause of fever in children so that appropriate treatment can be initiated as soon as possible. Otherwise, serious complications may arise when the immature immune system of a child is overwhelmed by the underlying disease. Most cases of fever in children are due to infections, teething and vaccinations. Infections of the respiratory system, gastrointestinal system and ear account for most cases of fever in children.

Perinatal infections are potential causes of fever in newborn babies. These infections are acquired by the baby either in the womb or during birth. The chances of acquiring infection during birth are high when the mother is suffering from a sexually transmitted disease (such as genital herpes). The following are some of the potential causes of fever in babies and children.

Read more on how to reduce a fever in children.

Respiratory tract infections

Viral and bacterial infections of the upper and lower respiratory tract are very common causes of fever in children. Symptoms of respiratory tract infections include coughing, sneezing, nasal congestion. difficulty in breathing, difficulty in swallowing, and a nasal tone in the voice. Examples of viral infections of respiratory tract include pneumonia, influenza, croup, common cold, and sinusitis. Examples of bacterial infections of respiratory tract include tonsillitis, pneumonia, whooping cough, pharyngitis and scarlet fever.

Gastrointestinal infections

Both viral and bacterial gastroenteritis can cause fever in children. Signs and symptoms of gastrointestinal infections include nausea, vomiting, diarrhea, abdominal pain and loss of appetite.

Ear infections

Ear infections are a common occurrence in children. Most ear infections in children occur in the middle ear and cause symptoms such as ear pain, discharge from the ear, impaired hearing, redness or swelling on the ear pinna and (sometimes) deafness.

Other infections

Infections of the respiratory tract, gastrointestinal tract and ear are the most common causes of fever in children. However, infections in other parts of the body such as mouth, arms, legs, urinary tract and nervous system also cause fever. General infections such as chickenpox, measles, mumps, rubella, malaria, HIV and hepatitis are also potential causes of fever in children.

Non-infectious causes

Non-infectious causes of fever in children include heat stroke, teething, vaccination, hyperthyroidism, autoimmune disorders, neurological disorders, cancer and chemical poisoning.

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