The immune system is the body's natural defense system that helps
fight infections. An impaired immune system does not work properly and can't
effectively protect a person against infection.
Some conditions and medicines weaken or impair the immune system.
These may include:
- Alcohol or drug abuse or
withdrawal.
- Certain diseases or conditions. Diabetes, cancer,
HIV/AIDS, or conditions in which the body mistakenly identifies its own tissues
as harmful (autoimmune disorders) are some examples.
- Chemotherapy
or radiation therapy.
- Some medicines, such as corticosteroids or
those taken to suppress the immune system after an organ
transplant.
- Surgery to remove the spleen (splenectomy).