That is one of the most frequently asked questions in medicineand the experts disagree.

Matthew Kluger, vice president for research at the Medical College of Georgia and a fever physiologist, said that animal studies suggest that fever is beneficial. Fever is so “costly” in metabolic terms in humans, each 2 degrees Fahrenheit of fever raises heart rate by 10 percent that fever probably never would have evolved in the first place unless it did more good than harm.

In ferrets given influenza, those who were treated with aspirin had more virus in their nasal secretions than those whose fevers were left untreated. Other animal studies suggest that treating fever may even increase the mortality rate. “One can’t do [such] studies in humans,” Kluger said, “but if you extrapolate this to humans, it suggests that moderate fever is protective.”

On the other hand, leaving a fever untreated may make you feel miserable and treating an illness with Tylenol, aspirin or ibuprofen is likely to prolong it by a few hours at most, Kluger said.

Dr. Michael Shannon, chief of emergency services at Children’s Hospital Boston, comes down firmly on the side of treating fever. “Your immune system will keep fighting the infection, whether or not you bring the fever down with medications.”

When infection occurs, the immune system pours out chemicals called cytokines, including interleukin 1 and interleukin 6. These natural fever-makers trigger a cascade of other chemicals, including prostaglandins, which act on the brain to raise the body’s thermostat, or set point. At the end of an illness, other chemicals called cryogens, or antipyrogens, bring it back to normal.

If you’re an adult, call a doctor if your fever is 103 degrees Fahrenheit or higher. With a newborn, call the doctor for any temperature over 100.4. With an older child, call the doctor if the temperature is 102 or higher.

As for medications, take them if you want.