What is fever? 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 infection, eating, physical activity, medications, surrounding (room or outdoor) temperature, or a strong emotional response. 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. An extremely high fever can lead to seizures (called a febrile seizure) in children. These seizures do not usually cause permanent harm, but you should visit your health care professional if your child experiences a seizure. Seek emergency care if a seizure lasts more than a couple of minutes. If your fever lasts more than 48 hours, is associated with other alarming signs, or causes you concern, seek prompt medical care. Fever in infants and very young children can quickly become serious, so exercise caution if your baby develops a fever. Seek immediate medical care (call 911) if you, or someone you are with, have a fever with excessive crying, difficulty breathing, stiff neck, or confusion. These are signs of a serious or life-threatening illness that should be immediately evaluated in an emergency setting.