Fever in Infants

Fever in infants is an immediate concern, especially in younger infants. This is not because the fever could cause harm, but for other reasons:

  • Infants are more prone to serious infections, like sepsis (infection of the blood), meningitis (infection of the fluid around the brain), and pneumonia than are older children.
  • Infants may not show any other signs of serious infection.

The most significant things are the age of the infant and the height of the fever.

Infants 2 months of age or younger with a fever over 100.5 (rectal) should be seen immediately (even in the middle of the night). If you have any question, please call immediately!

  • Don't wait. While it may seem embarrassing to have a child seen in the ER for just a fever, but it is far better to feel awkward than to stay at home when your child has a dangerous infection. Don't be apologetic about bringing your child in; the best-case scenario is that you are over-reacting.
  • Don't panic. Most infants with fever are sick with minor problems, so you don't have to panic.

Infants between 2 and 6 months of age should be seen immediately if they have other serious symptoms.

  • Lethargy (difficulty to arouse) or Irritability (difficulty to comfort) - This is a judgment call, but it is a significant sign.
  • Cough, shortness of breath, abdominal swelling, or diarrhea

If your child appears reasonably well to you in this age, you can probably wait to see what develops:

  • Infants from 2-4 months should prompt a message or phone call to let the doctor know about the fever.
  • Infants from 4-6 months can wait as long as the child looks OK. Fever lasting more than 3 days should also prompt a message or phone call.

Infants over 6 months can be treated the same as older children.

Since fever is more serious in infants under 6 months of age, do not treat fever with medication (unless otherwise directed) or warm baths. It is an important symptom to follow.

Fever in Children

For children under 6 months of age, see also Fever in Infants


The definition of fever is a core temperature over 100.4 F (38.0 C). Technically, there is no such thing as a low-grade fever.

How to take a temperature

It is very important to get an accurate temperature that estimates the core temperature.

  • Rectal Temperature - this is the most accurate way to take a temperature (but least popular). If a fever is suspected in a child under 6 months of age, a rectal temperature should always be done (see Fever in Infants).
  • Oral Temperature - this is also a fairly accurate way to take temperature, but impossible in infants and difficult in young children.
  • Axillary (underarm) Temperature - This is the least accurate way, but it is easy. It is only recommended as a last resort.
  • Ear Thermometer Devices (and others) - these are somewhat more accurate than axillary temperatures, but are still not great. They are by far the easiest, and can be done quite quickly. They give a rough estimate of a child's status in this regard.

When to take a temperature

In general, people with significant temperatures act differently (lethargy and excessive irritability in children) than those without. 

When to worry about fever

By itself, fever is not a worry (except in Infants). The body temperature going up is a tool the body uses to help fight infection, so more serious infections (like pneumonia or sepsis) are associated with higher temperatures. More than the hight of the fever, the main reasons to be concerned about fever are the other symptoms the child is having. Here is when most doctors would be more concerned:

  • Fever of 104 F and above
  • Fever with other symptoms:
    • Shortness of breath (could signify pneumonia)
    • Significant drooling or inability to swallow (could signify serious throat infection)
    • Abdominal pain (along with a high fever, could be serious)
    • Lethargy - Anyone with a fever with be tired, but a child who is difficult to arouse, or with significant confusion, may have a more serious infection.
    • Fever which lasts more than a week.

Are fevers dangerous?

No. Fevers do not, by themselves, cause harm to the child with the fever. Specifically, fevers do not:

  • Cause brain damage
  • Cause seizures (except in children who already have a predisposition to seizures)

Children with fever are threatened by the things causing the fever, not the fever itself. 

What to do about a fever.

There is no medical reason to treat a fever. The only reason to treat it is to make the child feel better (which is a reasonable justification, but won't heal them quicker). So,

  • If your child seems well, you do not need to treat the fever.
  • If your child is an infant, read the guidelines for fever in infants and do not treat the fever unless otherwise directed.
  • There are two medications for fever,
    • Acetaminophen (Tylenol, etc)
      • Lasts for approximately 4 hours
      • Has very little toxicity if taken in the proper dose range
      • Is not more effective if taken over recommended dosage
      • Is dangerous (and even lethal) if taken in significant overdose.
      • Despite the danger of overdose, this is the first choice drug, as it takes a dose significantly above the recommended range.
    • Ibuprofen (Motrin, Advil, etc.)
      • Lasts for 6-8 hours.
      • Is more effective than acetaminophen in lowering the temperature, but can have more side effects.
      • Stomach problems, and even kidney problems occur if used in doses over the recommended range, or if used on a regular basis.
      • Can be used in combination with acetaminophen if needed.

See Pediatric Medication Dosage Guide.

There is no evidence that giving a warm/cool bath helps at all, is associated with significant discomfort, and could cause problems.

When to Contact our Office

If after reading this you are still worried, please contact our office immediately.