Fever in Children: What to Do, When to Worry

Chris Yun, MDby Chris Yun, MD
Fever in Children: What to Do, When to Worry

Fever in Children

A fever is a rise in body temperature. Any temperature of 38 degrees Celsius (℃) or 100.4 degrees Fahrenheit (℉) and higher in children counts as a fever – this is usually a normal and even helpful response to illness.

Table of Contents:

  • What causes fever?

  • Taking your child’s temperature

  • Fever home care for children

  • When to see a doctor

  • FAQ

What causes fever?

Fever is only one aspect of the body’s defense mechanism against infection. When foreign pathogens like viruses or bacteria are detected, the immune system activates in several ways. One way is by raising your body temperature, since viruses and bacteria can only multiply within a certain temperature range.

Pretty much every type of infection can cause a fever – there is no point in listing all of them! In children, the vast majority of fevers are caused by what are collectively referred to as “the common cold” – relatively harmless viruses that the immune system handles on its own in several days. The pediatrician’s job is to make sure your child’s fever is not caused by something that requires more investigation or specific treatment, like strep throat, urinary tract infections, pneumonia, or certain cancers. Later on in this article, we will describe the “red flag” symptoms that accompany fevers that would prompt a pediatrician to want an in-person evaluation. 

So, fevers in children are a healthy sign of a robust immune system. However, it’s important to note that fevers in children under 3 months old should always be evaluated by a doctor because their immune systems are still immature and even “regular” viruses and bacteria can be dangerous.

Taking your child’s temperature

While parents can typically identify fevers simply because their child feels warmer than usual, thermometers are always more accurate. There are several types of thermometers and several methods of taking your child’s temperature.

From the AAP:

“Temperatures taken rectally or orally are more accurate than those obtained using the axillary or tympanic methods. If your child is younger than 3 years old, a rectal temperature gives the best reading. At around 4 or 5, you can feel comfortable taking a temperature by mouth.

A normal temperature for a child may range from 97 degrees Fahrenheit (F) to 100.4 degrees F. In general, the AAP considers anything over 100.4 degrees F to be a possible fever.

Taking a rectal temperature:

  • Clean the end of the thermometer with rubbing alcohol or soap and water; rinse in lukewarm water and dry. Apply a small amount of lubricant, such as petroleum jelly, on the end.

  • Place your child tummy down across your lap. Hold the child by placing your palm against his lower back. Or, place the child face up and bend his legs to the chest. Rest your free hand against the back of the thighs.

  • With the other hand, turn the thermometer on, and insert it ½ to 1 inch into the anal opening (not too far). Hold the thermometer in place loosely with two fingers, keeping your hand cupped around your child’s bottom. In about a minute, when you hear the beep, remove it and check the reading.

  • Re-clean. Be sure the thermometer is labeled so it’s not accidentally used in the mouth.

Taking an oral temperature:

  • Wait 15 minutes after the child has been eating or drinking before taking a temperature.

  • Clean thermometer. Turn the thermometer on, and place the tip under the tongue toward the back of the child’s mouth. Hold in place for a minute until you hear a beep.

Taking an axillary temperature:

  • Turn on the thermometer, and place the small end in your child’s armpit (thermometer should touch skin, not clothing).

  • Gently hold the arm in place until the thermometer beeps.” 

Fever home care for children

There’s plenty you can do for your sick kids, from chicken soup to free reign on the TV. But more importantly, since fevers tend to dehydrate children quicker, push water and other fluids, keep them home from school or daycare, and let them cuddle and rest. 

How to reduce your child’s fever

While fevers are not dangerous, they can make your child feel crummy. In that case, you can use one or both of the following over-the-counter medicines:

  • Ibuprofen (aka Advil or Motrin). It is not recommended for infants under six months old. 

  • Acetaminophen or Paracetamol (Tylenol)

Strictly follow the recommended dose. Use a correct measuring device. Avoid using a spoon as it could be inaccurate. In case of doubt about the dosage, or if your child is younger than 2 years, call your doctor and ask about the dose that must be given.

Also, if your child has a fever but is sleeping comfortably, it is not worth it to wake them up just to administer medicine. Not only does it interrupt their rest, but in addition, lowering their fever will not help them recover faster.

Also, never administer aspirin (salicylates) or associated products to a child unless specified by the doctor, as aspirin can cause a rare but serious condition, Reye syndrome, that is known to cause severeliver damage.

Helping your child feel better

Other ways to help your child feel better:

  • Let them dictate how warm or cool to make the room, or how many layers they want to wear. Since their bodies want to raise their internal core temperature, they may feel shivery and cold and demand more external heat to help the body raise its temperature even more. Do not assume that bringing their fever down with cool baths or open windows or less layers is a good idea.

  • Offer them food if they want it, but do not be alarmed at a very low appetite.

  • Feed them lots of water, soups, flavored gelatin, or ice pops. Cola, tea, caffeinated, and carbonated or fizzy drinks should be avoided as they can worsen dehydration.  In general, plain water is just fine. Pedialyte or other electrolyte-containing liquids are not necessary unless directed by your child’s doctor.

When should I call the doctor?

Here are the following circumstances under which the fever might not be caused by the common cold, and warrant an in-office evaluation.

  • Your infant of 3 months or younger has a rectal temperature of 100.4°F (38°C) or higher (these infants should be evaluated in a pediatric emergency room)

  • Your child has a temperature of 100.4°F (38°C) or higher and they have a weakened immune system, such as with diseases like sickle cell disease or cancer (these infants should be evaluated in a pediatric emergency room)

  • Shows signs of dehydration

  • Is inconsolably cranky/fussy

  • Has 3 days in a row of fever, especially if there are no other symptoms like cough or runny nose

  • Refusal to stand up or walk

  • Stiff neck

  • Severe headache, especially with vomiting

  • Inability to swallow

  • Seizures or fainting

  • Flat, red pinprick dots on the skin

Frequently Asked Questions

Are some kids’ fevers OK?

In most cases, a mild fever lasting up to about 3 days shouldn’t cause worry. Children 3 months and older with a fever but who are still drinking, smiling, alert and active can be safely watched at home. 

How high is too high a fever?

In the past, higher fevers (over 104 F) were associated with more serious illnesses like pneumonia. However, due to routine infant vaccinations, the number of bacterial illnesses in children have declined significantly and now there is no clear correlation between height of fever and severity of illness. Still, if your infant is less than 90 days old, you should immediately contact their doctor. And even if your child has a benign fever of 104, they will likely be quite uncomfortable and could use a dose of acetaminophen or ibuprofen to make them feel better.

The duration of fevers (how many days in a row your child has fevers) is more important than how high the fever spikes. 

How long should a child’s fever last?

Children’s immune systems typically make fevers last no more than 3-5 days. If it goes on longer than that, seek care to rule out more serious causes of fevers.

Do fevers cause seizures?

This is a very good question. It is not uncommon for children under the age of six to have “febrile seizures” either during or right before a fever spikes. The vast majority of these seizures, while scary, are not dangerous and do not cause long term problems. These typically last up to fifteen minutes. If one happens, make sure that your child is still able to breathe and seek care at an emergency room.

However, the evidence is unclear if it’s the fever or the underlying illness which causes the seizure. Often, children sick with colds have “febrile seizures” even if they never spike a true fever. This is why it is not strongly recommended to lower children’s fevers simply in order to reduce their risk of having a febrile seizure – even if they have had one in the past. Talk to your child’s doctor for more information on this topic.

What about if my child’s fever goes up and down all day, or if it does not respond to medicines?

Fevers are supposed to wax and wane throughout the day. They typically spike highest in the evening and night. This is the reason that most parents schedule sick visits for their children in the evening, but by the time they bring their child into the clinic the next morning, the child looks peachy. But from a pediatrician’s perspective, ANY fever in a 24 hour period counts as a “day of fever”. You do not need to keep a detailed hour-by-hour schedule of how the fever changes.

In addition, while acetaminophen or ibuprofen generally lower fevers, their main role is to make the child feel more comfortable, not to keep the child’s temperature under an arbitrary number. Like other medicines, they are not 100% effective. It is not an ominous sign if the fever does not go down even after a dose of medicine. Still, call your child’s doctor if you are concerned.

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