Fever: How High is Too High?

Despite having fever information on our website and blogging about it many times, parents often call in or bring their child in with excessive concern for fevers. (Note: paracetamol is the same as acetaminophen and Tylenol in the linked article.)

The information here is only for infants and children over 3 months who are otherwise healthy and vaccinated. If those criteria are not met, the child is in a higher risk category.

Fever is one of the biggest anxiety inducers in parents, and I want that to change. Yes, we should care for our children when they're sick, but we don't need to worry about the numbers on the thermometer.

Maybe one time I'll explain fever in a way that hits home so parents can stop focusing on the number and more on the child. Parents often tell us in detail what the temperatures are at various points of the day but omit how the child looks and acts. I care more about the child's behaviors than the thermometer's reading.

I know fever is scary. Kids are miserable. But the temperature itself is not what we treat. Treat the symptoms!

What is a fever?

The number on the thermometer can be confusing to parents. How the temperature is taken is as important as the number itself to determine if it is a fever. A fever is often defined as a temperature over 100.4 °F (38 °C) but it can vary based on how you take the temperature (rectal vs oral vs forehead). This is simply the minimum temperature that is no longer considered normal.

The American Academy of Pediatrics doesn't recommend treating fevers until the temperature is over 102°F unless the child is uncomfortable. Thermometers are not very accurate, so when you worry more about a temperature that is half of a degree higher than another temperature, it might not be a significant difference. You could take the temperature twice in a row and get different readings. If your child is playful and the thermometer reads 101.5°F that is a very different story than if your child is barely moving, whimpering, and breathing fast with a temperature of 101.5°F. I wouldn't recommend any fever reducers for the first, but I would recommend the second get evaluated by a pediatrician or other medical provider.

Why do we care about fevers?

I think medical professionals help to foster this fear of fevers because we ask about them. It can be helpful to know the actual temperature because many kids are warm but not really running a fever.

• We are more contagious during a fever, which is why schools and daycares won't let kids stay if they have a fever.

• The height of the fever doesn't indicate if the child has an infection requiring antibiotics or not, but it can cause increasing discomfort as it rises above 102°F.

• The height of a fever itself does not cause fever seizures, but a rapid change in temperature can cause a seizure in a child that is susceptible to them.

• If a true fever lasts more than 3-5 days or is accompanied by other concerning symptoms, the child should be seen to look for a source.

So how high is too high?

Fevers higher than 106°F (41°C) might be the answer parents are asking for when they want to know what temperature is too high. It is at this point that brain damage from the temperature itself can occur due to hyperpyrexia (heat stroke). This is not common from a simple infection and other symptoms will be present, such as change in consciousness, vomiting, flushed skin, headache, rapid breathing, and very rapid heart rate. Emergent medical attention and cooling the body is important with hyperpyrexia, which differs from fever.

If your child does not appear very ill and the thermometer reads very high, it's likely the thermometer is in error.

What if the temperature doesn't go down to normal after using a fever reducer?

When parents give a fever reducer, they often worry that the temperature doesn't go back to normal. Returning to normal doesn't mean it isn't a serious infection and not returning to normal doesn't mean that it is a serious infection. Studies show the temperature tends to decrease by 1.8 to 3.6°F.

• Acetaminophen begins to work in 30 - 60 minutes and has its peak effect in 3-4 hours. The duration of action is 4-6 hours.

• Ibuprofen begins to work in under 60 minutes and has its peak effect in 3-4 hours. The duration of action is 6-8 hours.

The goal should be to make a child more comfortable, not to get the temperature to normal.

My personal opinion is that most children won't need their temperature taken to verify that they are better after a fever reducer. They should be more comfortable. If they aren't, then it's wise to have them evaluated professionally.