Top of the page
The immune system is the body's natural defence system that helps fight infections. The immune system is made up of antibodies, white blood cells, and other chemicals and proteins that attack and destroy substances such as bacteria and viruses that they recognize as foreign and different from the body's normal healthy tissues.
The immune system is also responsible for allergic reactions and allergies, which may occur when the immune system incorrectly identifies a substance (allergen), such as pollen, mould, chemicals, plants, and medicines, as harmful.
Sometimes the immune system also mistakenly attacks the body's own cells, which is known as an autoimmune disease.
Current as of: September 23, 2020
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Brian D. O'Brien MD - Internal Medicine & Adam Husney MD - Family Medicine & Peter Shalit MD, PhD - Internal Medicine & Elizabeth T. Russo MD - Internal Medicine
To learn more about Healthwise, visit Healthwise.org.
© 1995-2021 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.