Anergy is a term meaning the lack of strength or the failure of the body to respond to an allergen or antigen or any substances that normally would provoke an antigenic response.

This is a term used in immunology. Anergy toward self-targets functions as one self-tolerance mechanism monitoring the auto-reactive cells found in autoimmunity. Clonal deletion where lymphocytes die if they identify a self-antigen during their maturing in the bone marrow or thymus gland is a main device for the inhibition of autoimmunity.