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Ask Dr. Dina: What causes a fever and how can I treat it?

Flushed cheeks, hot forehead, shivers—your kid has a fever. Now what? Dr. Dina Kulik has all the answers.

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Boy with fever checking temperature

Photo: iStockphoto

Kids look and feel downright awful when they have a fever: They’re sweaty, shivering and lethargic. It scares a lot of parents. In fact, at this time of year, fevers are the most common thing I see. Here’s what you need to know.

What causes a fever?
A fever occurs when the area in your brain called the hypothalamus—the body’s thermostat—shifts the set point of your body temperature higher. This often happens as a result of a cold, virus, bacterial infection or heat exhaustion, or after immunizations. (Teething can elevate your body temperature, but not to the point of what’s considered a fever.) While it’s worrisome when your little one is burning up, remember that a fever is your body’s natural response to infections—it is helpful. A fever helps the body release more white blood cells and antibodies, which also fight off the nasty bugs.

How do I best treat a fever?
When your kid has a fever, he’ll likely feel cold, shiver, seem sluggish and generally look unwell. Some kids with fevers, however, continue to run and play just as they normally do. If your kid looks and feels well, I wouldn’t rush to try to bring down his temperature—treat the discomfort, not the number on the thermometer. Acetaminophen and ibuprofen are great fever reducers, and I like to offer these medicines if a child is uncomfortable. Never give acetylsalicylic acid, like Aspirin, to anyone under age 18, as it poses a risk of causing Reye’s syndrome, and liver and brain dysfunction. Make sure your kid is drinking small amounts of fluid frequently and getting plenty of rest: nature’s best medicine.

With liquid pain medications, should I go by age or weight?
The package instructions are so confusing—especially at 3 a.m. Acetaminophen is measured at 15 milligrams per kilogram (your child’s weight) every four hours, and ibuprofen at 10 milligrams per kilogram every six hours. It’s best to determine the dosage by weight. The age cut-offs can be especially confusing if your kid is either heavy or light for her age. At your next doctor’s appointment, ask for your child’s weight and make a note of the proper dosage right on the box. That way, at 3 a.m., you’ll know exactly how much to give. Always use the measuring tool that comes with the medicine to avoid any dosing errors. You shouldn’t give acetaminophen more than once every four hours, and never administer more than five doses in a 24-hour period, as it’s hard on the liver. And ibuprofen should not be given more than once every six hours and never more than three times in a 24-hour period; doing so can cause kidney damage.

Is a high fever more serious?
How your kid is acting is often a better indicator of how severe the illness is than the number on the thermometer; whether it’s 38C or 40C, my treatment will be the same. A fever isn’t dangerous until it is above 41C (105.8F). Extreme temperatures tend to happen with medicine overdoses and heat stroke, not illness. But kids with very high temperatures need to be taken to the hospital; cooling techniques will be required. A high fever won’t bring on a seizure; some kids simply have a propensity for having seizures, and the threshold is lowered when there is a fever.

What should I do if my kid has a febrile seizure?
Febrile seizures are common, occurring in up to five percent of kids. Seizures are essentially “misfires” in the brain that cause convulsions and loss of consciousness. Typically, a seizure happens when a kid has a viral infection, his temperature spikes and his seizure threshold is lowered. A child will convulse, shaking his arms and legs, and his eyes will roll back. Some will have incontinence, fall or bite their tongue.

I’ve seen thousands of children have a seizure in front of me in the emergency room, and it always looks scary. If your child has a febrile seizure, try to think clearly and take note of the time. If the seizure lasts longer than three minutes, call 911. This is uncommon—they are typically shorter in duration. Lay your child on her side (in case she vomits) in a safe, soft space. Don’t put anything in her mouth—I have seen parents’ fingers bitten off! Your kid will likely be sleepy for 30 to 60 minutes afterward. It’s important to make a follow-up appointment with your kid’s doctor if he has a seizure. Often, a viral or common bacterial infection like an ear infection is the cause of the fever, and a bacterial infection can be treated with antibiotics. There is no need to go to the emergency room if your child returns to normal within an hour and is otherwise acting and feeling OK.

When should I worry about a fever?
In babies three months and younger, a fever can signify a serious illness, like meningitis. If your baby has a fever, see your doctor or go to your nearest emergency room immediately. As the doctor will want to examine your baby first, don’t give any fever-lowering medicines. If your kid is four months or older, seek medical assistance if the fever lasts for more than 72 hours; if your child is vomiting excessively, is dehydrated, or has a strange rash. And before rushing to your doctor or emergency room, I suggest trying the appropriate dose of acetaminophen or ibuprofen and waiting 30 minutes. If your child looks much better, and is interactive and able to drink, you can likely wait it out for a bit.

Dr. Dina Kulik is a paediatrician and emergency room doctor in Toronto, and mom to three boys, who are six, four and two. Send your kids’ health questions to editors@todaysparent.com

A version of this article originally appeared in our January 2017 issue, pg. 30.

Read more:
Fast fever facts
How to know when your kid is too sick for school
How to treat a fever at home