Most people have a body temperature of around 98.6° F (37° C), and it stays pretty much the same from day to day— until germs enter the picture. Microorganisms beware! The body’s defense system puts on the heat in an attempt to cook the germs right out.

Hot and Bothered — Why It Matters

The hypothalamus, at the brain’s center, acts as the body's thermostat. So when the hypothalamus gets word that germs are on the scene, it starts to set the body's internal temperature higher. The heat helps fight the germs by making the body a less comfortable place for them to hang out Molecular+basis+of+fever+in+humans++Dinarello,+C.A.,+Wolff,+S.M.+American+Journal+of+Medicine,+1982+May;72(5):799-819.. And certain cold viruses don’t reproduce at higher temperatures, so even a slight fever can actually help to get rid of the virus more quickly.

A fever indicates the body has gone into fight mode to get rid of a virus or infection Fever,+fever+patterns+and+diseases+called+'fever'+a+review.+Ogoina,+D.+Immunology+and+Infectious+Disease+Unit,+Department+of+Medicine,+Bingham+University+Teaching+Hospital,+Jos+Plateau+State,+Nigeria.+Journal+of+Infection+and+Public+Health,+2011+Aug;4(3):108-24.+Epub+2011+Jun+14.. Almost any infection can cause a fever— measles, chicken pox, strep throat, influenza, and even the common cold often cause an increase in body temperature. In case burning up isn’t bothersome enough, a fever sometimes comes with other symptoms like chills, loss of appetite, an overall feeling of tiredness or weakness, and headaches Fever,+fever+patterns+and+diseases+called+'fever'+a+review++Ogoina,+D.+Immunology+and+Infectious+Disease+Unit,+Department+of+Medicine,+Bingham+University+Teaching+Hospital,+Jos+Plateau+State,+Nigeria.+Journal+of+Infection+and+Public+Health,+2011+Aug;4(3):108-24.+Epub+2011+Jun+14..

Fever Deceiver — The Answer/Debate

There are several ways to measure body temperature, including thermometers that go in the mouth, under the armpit, in the ear, and in the rectum. The rectal method is the most accurate, but don’t get too grossed out— infants benefit most from this technique. A thermometer in the mouth is the next best way, while the armpit and ear give the least accurate readings. And leave those mercury thermometers to the Smithsonian Museum— digital thermometers make life a little easier .

Get out the glasses and check the number on the screen: Fever temperatures normally run around three to four degrees higher than normal body temperature. In general, don’t treat fevers below 102° F (38.9° C) with any medication (even common over-the-counter meds like Advil) unless a doctor recommends it. Medicine like ibuprofen and acetaminophen can help ease the symptoms that accompany a fever, but they don’t treat the underlying condition. And since medication blocks the signals that tell the hypothalamus to crank up the degrees, those germs may live to fight another day Fever+in+Children:+Should+it+be+Treated? +Habbick,+B.F.+Canadian+Family+Physician+Medicine,+1988+May;34:1161-4..

If a fever runs any higher than 102° F, or it lasts longer than three days, medical attention may be necessary. Fevers can pose the greatest risk to infants, pregnant women, and individuals with compromised immune systems , so it’s important for them to take a germ turf war seriously Review:+Hyperthermia+and+fever+during+pregnancy.+Edwards,+M.J.+Faculty+of+Veterinary+Science,+The+University+of+Sydney,+Mosman,+New+South+Wales,+Australia.+Birth+Defects+Research+Clinical+Molecular+Teratology,+2006+Jul;76(7):507-16..

As for everybody else, when the body warms up, it’s easy to get dehydrated, so drink extra fluids to compete with the heat. Here’s the good news: After the cause of the fever disappears, the hypothalamus sets everything back to a normal temperature, and the body should be not-too-hot-to-trot.