What is a fever?
A fever is a body temperature higher than normal, usually 38 degrees Celsius (100.4°F) or above. It is a natural sign that the body is fighting an infection.
When germs invade, the immune system releases chemicals that tell the hypothalamus, the brain's thermostat, to raise body temperature. A higher temperature can make it harder for some bacteria and viruses to multiply and helps immune cells work better. Shivering and feeling cold at the start of a fever are the body's ways of heating up.
Normal body temperature varies between people and through the day, but it is usually around 37 degrees Celsius. Most fevers are caused by infections such as colds, flu and ear infections, and they usually go away in a few days. Rest and fluids help, and medicines like paracetamol or ibuprofen can relieve discomfort.
When to seek help
Medical advice should be sought for a fever in babies under three months, a very high fever, a fever lasting more than a few days or one with symptoms like a stiff neck, rash, confusion or difficulty breathing. Doctors can check for serious infections.
Did You Know?
Some animals, including lizards, raise their body temperature when sick by moving to warmer places, a behavior called behavioral fever.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.