Childhood Fevers Demystified: What Parents Really Need to Know

Every parent has been there at some point; you go to soothe your fretful child and realize they are burning up with fever. What do you do next? Stanford Medicine Children’s Health pediatrician Patty Sabey, MD, is here with the answers you need to manage your child’s fever.

What is a fever?

A fever may seem scary, but it’s just how our bodies fight infection. The body increases its natural temperature (average 98.6 F and normal range 97.7 F to 99.5 F) to help kill the germs that are causing an illness.

“Fever is a result of the immune system being activated to fight the infection. There are different chemicals in the body’s immune system that trigger a chain reaction. For example, if you encounter a virus, there is a cascade of events that results in the release of certain chemicals, and that in turn leads to a fever,” Dr. Sabey shared. “It allows the immune system to function optimally. In other situations, like when it’s noninfectious, the fever could be due to inflammation.”

Dr. Sabey explained that a child’s temperature usually has to reach a certain level before it is considered a fever.

“The definition of fever for all ages is 100.4 F or higher, or 38 C or higher,” she said. “But for infants younger than 3 months, any fever should be confirmed by a rectal thermometer, and they should be seen by a medical professional promptly. Fever is usually less concerning in an older child unless it is persistent, accompanied by other concerning symptoms, or exceeds 102 to 103 F.”

How to get an accurate temperature reading

When it comes to taking a child’s temperature, the right tools are key. Dr. Sabey recommends using a digital thermometer rather than the old-fashioned glass thermometers with mercury inside.

“Digital is the best. For all ages, you could start out with an ear thermometer, or you can try the armpit or forehead scan thermometer,” she said. “But if the temperature is near 100.4 F, then it’s best to confirm with an oral reading. Young infants may need a rectal thermometer.”

Just keep in mind that if your child is mouth-breathing because of congestion, you may get a lower reading. You can retest again after a few minutes to confirm that you are getting an accurate reading.

Getting an accurate reading helps doctors decide on the next step.

“Depending on the temperature, there is an increased risk of a serious infection manifesting with a fever,” Dr. Sabey said. “That’s why it’s important to get an accurate temperature so we can assess the potential risk and next step, which could be a trip to the emergency room or potential evaluation.”

What to do if your child has a fever

If your child does have a fever, the best course of action depends on their age, symptoms, and overall condition.

“If the child looks well and the fever is very mild, usually under 101 F, you don’t have to treat the fever right away. You can monitor and just check it in half an hour to an hour,” Dr. Sabey said. “If it’s 101 F or higher, generally, we would like to treat the fever to bring the temperature down because when you get to a higher temperature, there is also a risk of febrile seizure in young children. So, we want to control the temperature to prevent that.”

For example, Dr. Sabey explained that if a baby has a fever within a couple of days after getting vaccinations, and it is mild, you could manage it with acetaminophen or, for children 6 months and older, ibuprofen.

Alternating acetaminophen and ibuprofen may be recommended in some cases when a fever is difficult to control. Treating fever can also help the child to be more comfortable so they are able to eat and rest, making it easier for the child to recover.

“We alternate medications because sometimes one medication seems to work better than the other,” Dr. Sabey said. “But sometimes, it’s because the fever doesn’t respond right away, and it takes both medications to control the fever.”

However, Dr. Sabey shared, you don’t necessarily have to medicate around the clock if your child’s fever seems manageable.

“If you treat with a fever-reducing medication and the fever comes down very easily, and the child perks up, is eating, drinking normally,” she said, “you can continue to hydrate the child, monitor, and let it run its course.”

Ensuring proper hydration is crucial. Fevers can cause increased fluid loss, so offering small sips of water, breast milk, formula, or electrolyte solutions is critical. If an older child refuses to drink, frozen electrolyte pops or fruit-based Popsicles “could be used” to “help them” stay hydrated.

When to contact your pediatrician

Infants under 3 months with a fever should be evaluated by a pediatrician as soon as possible. Babies under 4 weeks require immediate medical attention. Consult your doctor if fever persists for more than 24 hours for children 3 to 24 months, or more than three days if they are 2 or more years old.

Signs that require urgent medical care:

Seizures associated with fever.

Signs of dehydration (dry mouth, absence of tears, decreased urine output).

Difficulty breathing or persistent coughing.

Vomiting that prevents fluid intake.

Fever lasting more than five days.

High fever (103 F or above) that does not improve with fever-reducing medication.

Fever after prolonged exposure to heat (could indicate heat exhaustion or heatstroke).

Inconsolable fussiness in an infant.

“Another thing to consider is that if the child has other concerning symptoms, or if the child looks sick, even if the fever is mild, it’s important to get help,” Dr. Sabey advised.

You know your child best, so Dr. Sabey urges parents to go with their gut and check in with their doctor if there are any concerns.

For more advice from Dr. Sabey, read A Parent’s Guide to Dealing With Head Lice or Get Your Child Ready for School With a Yearly Well Visit.