Many people think that a "fever" is any temperature above 98.6 degrees Fahrenheit (equal to 37.0 degrees Celsius).
It turns out, though, that our temperatures change constantly during a normal day. We tend to be cooler when we're asleep (especially at night), and warmer when we're awake and active. The "thermostat" in our brain, which controls blood flow to the skin (more when we're warm, less when we're cool), sweating (also more when we're warm and less when we're cool) and shivering (we shiver when we're too cool), tries most of the time to keep our temperatures between 97.5 and 99.5, and usually does a pretty good job of it.
When we are sick, whether from an infection or from other causes, our thermostats turn the temperature up. This actually helps when you have an infection: a fever helps your body get rid of bacteria and viruses, many of which will grow well at normal body temperatures but not at the higher temperature of a fever. Thus it's not always a good idea to try and bring down a fever all the way.
Of course, fevers do make you uncomfortable. More important, high temperatures can cause problems, including seizures in some people (although seizures don't usually happen unless your temperature is 104-105 or higher). Unless your doctor tells you to, don't try to bring your child's temperature all the way down to 98.6, because that may actually prolong the illness by delaying your body's efforts to kill bacteria and viruses. We define "fever" as a temperature of 100.4 F or higher. Unless your doctor suggests it, you shouldn't give anything for fever unless your child's temperature is 100.4 or higher (and possibly not unless it's higher than 101). (As always, remember that not all doctors do things the same way; if your doctor gives you different advice, you should follow it -- after all, your doctor knows your child better than I can.)
How you take a temperature depends partly on how old your child is, and partly on the kind of thermometer you use.
The old-fashioned mercury-filled glass thermometer takes a long time to work.
They are also illegal in many areas. The reason is the mercury: mercury is
poisonous, and hard to clean up if it's spilled. Some communities now offer
free non-mercury thermometers to people who turn in their old mercury
thermometers, so that they can collect the mercury and dispose of it safely.
Also, mercury thermometers are made of glass, and broken glass is also
hazardous. If you have a mercury thermometer, you should dispose of it --
promptly and properly.
These come in many different shapes and sizes, but they all consist of a "probe" which produces an electric signal that depends on temperature and a display (usually in numbers) that shows you the temperature. They are almost all battery-operated (if you buy one, you should also get a spare battery or two), and very hard to break. They also register the temperature faster than glass thermometers, and beep when they have finished measuring the temperature. I recommend these thermometers especially for small children.
NOTE: The numbers and the decimal point on digital thermometers
are very pretty. That does not mean that a digital thermometer
is more accurate than a mercury thermometer, or than other kinds of
thermometers. The inexpensive digital thermometers sold in drugstores
can be less accurate than mercury thermometers, although the digital
thermometers we use in our offices are usually more accurate (and harder
to break, too). Don't assume that the digital thermometer will read a
temperature accurately just because it's digital.
These use electronic sensors to measure the temperature of the eardrum, which happens to be very close to the brain's thermostat. They are very fast, but have to be in the ear canal within sight of the eardrum, which makes them hard to use on small babies and children with curved canals. We use them a lot in offices and emergency rooms because of their speed, but they may not be all that great at home, and I personally don't use ear thermometers on small babies.
This is the easiest place for a temperature, especially for small children. Place the probe right in the armpit, and hold your child's arm down so that the probe is surrounded by arm and armpit. NOTE: when you take the temperature under the arm, do not add 1 to the temperature you see on the thermometer. This "correction" doesn't work with everybody. (I have seen babies who had unnecessary spinal taps because parents mistakenly added 1 to what was on the thermometer.) Instead, tell your doctor
Place the probe under the tongue, and as far back under it to one side or the other as you can. (The farther back under the tongue you have the probe, the faster and more accurate the measurement.)
First lubricate the probe with Vaseline. Then place the probe in the anus, so that the temperature-sensitive part of the probe is completely inside.
Follow the instructions that came with your thermometer (some models are different from others).
A baby less than 8 weeks old can have a fever for many of the same reasons that older kids and adults do, including viral colds and sometimes even stomach flu. The problem is that we cannot tell just by examining a baby whether the fever is caused by a virus or by a bacterial infection. At this age a baby doesn't have all the defenses against bacteria that older people have, and so they can end up with an overwhelming infection, or sepsis. To find out for sure whether a baby with a fever has or does not have a bacterial infection, we need to take samples (of blood and urine, and often of spinal fluid) and try to grow bacteria from them. This can take 2 days, but we have to start giving antibiotics right after taking the culture samples, or else if there is an infection we may not catch it in time. We probably give 95 children antibiotics for 2 days without having to for every 5 children who have infections, but the consequences of not giving antibiotics to the 5 children who need them are such that we take no chances with the other 95.
So, if your baby is less than 8 weeks old and has a temperature of 100.4 or higher, you need to call your doctor immediately. There may be circumstances (such as overbundling) where the high temperature does not mean there is something very wrong with your baby, but you should let your doctor help you sort it out. Many doctors want to see any baby under 3 months old with a fever: check with your doctor (when your baby is born) to see how s/he likes to handle a baby with a fever.
If your 2-month or older baby has a fever, Tylenol may be helpful
if the temperature is high (over 101, even over 100 if they are
uncomfortable). If you have any doubt that there
might be something serious causing the fever, call your doctor.
Fevers in children at this age can be sorted out a bit more easily -- especially since they're usually caused by bugs picked up from others, often other children. (As a rough rule of thumb, if your child is in day-care or school, you can expect him or her to to pick up something every 2 or 3 weeks.) Although many of these fevers are caused by viruses, and therefore cannot be treated with antibiotics, some problems, such as ear infections, are caused by bacteria and can be treated with antibiotics if needed.
One problem that is especially prevalent in this age group is that it's possible for a child with a high fever to have a seizure because of the fever. "High" in this case usually means 104 or higher, although rare children (often those with underlying seizure disorders) may have seizures with lower temperatures. If your child has a temperature of 104 or higher, and you can't bring the temperature down at home, call your doctor. We can suggest ways to bring the temperature down, and we can help you decide whether someone needs to examine your child right away. If your child has a seizure, with or without a fever, and has never had a seizure before, call your doctor or EMS immediately.
The most common treatment for fever is acetaminophen (Tylenol, Tempra, and many other brands). These come in several different forms, including drops, liquid, chewable and swallowable pills, and suppositories. Generally, if your child needs Tylenol, you can just give it according to the directions on the package. However, if you have any doubts about the proper dose of Tylenol, or any other medicine for your child, call your doctor and ask. I have not given specific doses here because I believe that information should come from your doctor and be tailored to your child.
Sometimes you may have trouble bringing your child's temperature down with Tylenol alone: if this happens, your doctor can suggest different doses for the Tylenol, or may suggest another medicine such as ibuprofen (Motrin).
Many of us have recommended a combination of Tylenol and Motrin, in alternating doses, on the theory that the two medicines in combination would reduce a patient's temperature faster and for a longer time than either one alone. This had not been proven in studies until recently; a study published in the Archives of Pediatrics and Adolescent Medicine (vol. 160, pages 197-202) in February, 2006 shows that alternating Tylenol and Motrin does keep temperature down better in infants and small children than does either Tylenol or Motrin by itself. However, the medical literature overall isn't firmly in favour of using both medications at the same time. As always, ask your doctor whether the two-medicine treatment is right for your child, and how much of each medicine to give.
Another old standby, which works quite well, is a lukewarm bath. The water must be lukewarm: if it's too cold, your child's body will reduce blood flow to the skin, and that may make his/her temperature go up rather than down. The proper temperature is whatever feels about the same as your skin does, and sponging your child with the water may work better than just putting him/her in the bath. (And never leave a child in the bath unattended!) It is also a good idea to give Tylenol or another anti-fever medicine before putting a child in the bath. Tylenol and other anti-fever medicines turn down the body's "thermostat" so that the body doesn't generate more heat while you are trying to take heat away with the bath. Therefore, the bath will work much better after Tylenol or another anti-fever medicine.
Never give a child (or anyone under 25 years old, for that matter) aspirin, unless your doctor tells you to. Aspirin in a child with certain viral illnesses (such as chickenpox and mononucleosis) can produce a very serious liver disease called Reye's syndrome which can in turn cause seizures. There are a couple of childhood diseases that need to be treated with aspirin, but they are relatively rare.
Many thanks to Erin Duchan, MD, for a very helpful discussion of the value (and lack thereof) of medication for treatment of fever in children.
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