When should I worry about fever?

What qualifies as a fever?

A child's body temperature is not a constant 98.6 degrees. During the course of a typical day, body temperature may vary almost two degrees above or below the 98.6 average. Fever is considered to be present if the body temperature is outside of this normal range. As measured by a rectal thermometer, a temperature of 100.4 or higher is considered to be a fever. Less than this is not a "low grade fever;" it's simply within the normal temperature range.

 Why does the body make fever?

When a healthy child begins to fight an infection, natural chemicals called pyrogens are produced. These pyrogens cause the body's temperature to go up, resulting in a fever. A fever means that the body has found an infection and is trying to fight it. In fact, we know the immune system works better when the body is at a higher temperature.

 Fever is a symptom of most common illnesses of childhood, including: colds, gastroenteritis ("stomach virus"), flu, sore throats, sinus infections, ear infections, chicken pox, and roseola. Fever can also be seen with more serious infections, such as pneumonia and meningitis. High fevers, up to 106 degrees F, can be present in both simple infections and in complicated infections. So, fever alone (or the height of the fever) can't tell us whether a child has a mild infection or a more serious one. Read our information sheet on how to take a child's temperature. Instead, we look at other things to find out what type of infection is causing the fever:

  • How long has the fever been going on? Most simple illnesses have fevers which last up to 96 hours, or four full days from the time the fever started. Fevers can be quite high during this time, but will go away after about 96 hours because the body will start to eliminate the infection. Fevers which last longer than this can still occur with simple illnesses. However, if a child has fever more than four full days, we recommend getting the child checked to make sure there is no complicating problem.
  • What other symptoms does the child have? Cough, congestion, runny nose, vomiting, diarrhea, ear pain, rash, sore throat, stomachache, wheezing, rapid breathing, bladder pain, and muscle pain are other symptoms which help us figure out what type of infection the child has.
  • How is the child acting overall? Children with simple, common illnesses may not feel much like eating big meals, may be cranky, and will sleep more than usual - just like sick adults. However, these children should also be able to play a little bit, drink some liquids, and communicate how they feel. Worrisome signs include: refusing all food or drink, lethargy, inconsolable crying, lying very still for a long time, not seeming interested in usual people or things, etc. As you might expect, we are less concerned about a child with a high fever who is acting okay than a child with a low-grade fever who is very lethargic.

Sometimes, the only way to rule out a more serious infection is to have the child seen in our office, and we will carefully examine the child for a source of infection. If you feel concerned that your child is acting very sick, let us evaluate him or her. However, if your child is otherwise okay besides the fever, it is usually fine to wait and let it run its course.

Most fevers in otherwise healthy children are caused by viruses. There are hundreds of viruses that cause fever, congestion, cough, runny nose, and sore throat. Since there are no vaccines for these viruses, getting them and letting them run their course is just part of childhood. Children can get six to eight colds and one to three episodes of vomiting and diarrhea a year. (That averages almost an illness a month!) For children in day care, this number can be even higher. Your doctor can confirm what viruses are "going around" the community at the time.

Fevers do not cause brain damage. In order to have brain damage due to overheating, the body's core temperature must exceed 107 degrees F. Fevers do not cause temperatures this high; brain damage due to overheating is caused by environmental causes (e.g. sunstroke.)

Fevers can cause harmless seizures in a small percentage of children. In 3-5% of children, a rapid rise in body temperature (rather than the height of the temperature itself) can trigger a brief, harmless "febrile seizure." While scary to watch, these seizures usually stop after just a few minutes. It is well documented that these children do not have any brain damage, mental retardation, or learning disabilities as a result. Febrile seizures tend to run in families, and 97% of children with them have no more seizures after age 6.

Fever only warrants immediate physician evaluation in four cases. If your child gets a fever in the middle of the night, you do not need to take him or her to the emergency room unless:

  1. Your child is acting very sick.
  2. Your child is an infant under the age of 2 months.
  3. You have refused to get recommended vaccinations for your child, putting him or her at increased risk for invasive bacterial disease.
  4. Your child has a weakened immune system, fro m cancer treatment, HIV infection, immunodeficiency, etc.

Unless one of the above cases is met, it is safe to treat fever at home. You can use either ibuprofen (Advil, Motrin) products or acetaminophen (Tylenol) products. Do not use aspirin, which in children with certain infections can cause a dangerous condition cause Reye Syndrome. Check to be sure you are giving the right dose for your child's weight. If you are also using a cough/cold product (Dimetapp, Robitussin, etc.), check the label to see if it contains acetaminophen. If so, do not give additional acetaminophen.