Patients battling the fever of a cold or flu are often advised to take aspirin, and sometimes to drink hot tea. Is that traditional advice sound? Not according to two British pharmacologists, Anthony Milton and Michael Dascombe of the University of London's School of Pharmacy. Aspirin does reduce high temperature, but caffeine—a stimulant present in tea, coffee and some types of cola drinks—appears to keep body heat up when taken in quantity. Thus the two substances cancel out each other's effects.
The pair made their initial observations on laboratory animals, injecting some with an endotoxin, a bacterial substance that produces fever, and others with an endotoxin-caffeine combination. Those receiving both developed higher fevers than those injected with the endotoxin alone. The researchers then tried treating the animals with an aspirin-caffeine preparation similar to those sold as patent cold remedies. The combination did not reduce temperature at all. A follow-up study with human volunteers confirmed the animal experiments. When 35 students received typhoid vaccinations, which produce a mild infection and fever, those who were given caffeine had higher temperatures than those who were not.
Doctors are not yet sure how caffeine raises fever or blocks aspirin's cooling properties. They speculate that caffeine may stimulate release of certain fever-producing hormones. But pending further study, they have some simple advice: fever sufferers should avoid tea, coffee and medications containing caffeine. To wash down aspirin, use water.