Fever is an increase in your body’s temperature to a range that is above normal (98.6 degrees Fahrenheit). Normal body temperature can change throughout the day by a few degrees. Various factors can increase your body temperature including eating, physical activity, medications, surrounding (room or outdoor) temperature, or a strong emotional response.
Part of your body’s natural defense response to infection is to raise the body temperature. Most pathogens survive best at normal body temperature. Therefore, raising the temperature is your body’s natural way of killing the infectious agent or preventing its spread.
An oral temperature of 99.5 degrees Fahrenheit in a child and over 99 to 99.5 degrees Fahrenheit in adults is considered a fever. Fever can be caused by fairly benign conditions, such as a cold, or by serious conditions, such as influenza and meningitis. Infant teething, recent immunization, autoimmune and inflammatory disorders, and some cancers can cause a fever as well.Learn more about fever ›