THE long-held belief that there is a 'normal' body temperature of 98.6F (or 98.4F in the UK) should be disregarded because temperatures vary according to the individual and the time of day, says a study published in the Journal of the American Medical Association.

The authors, from the Veterans Affairs Medical Center, Baltimore, Maryland, collected 700 oral temperature readings from 148 people at different times of the day over a four-year period, and found they ranged from 96F to 100.8F. The average temperature also varied depending on time of day, with a low of 97.6F in the early morning to a high of 98.5F in the afternoon. Women had slightly higher average temperatures than men.

The authors suggest that 98.9F in the early morning, and 99.9F overall, should be regarded as the upper limit of the normal oral temperature in healthy adults aged 40 or younger.