the immune system is the body's natural defence 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:
- substance use disorders or problems caused by quitting their use (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).