What is anaphylaxis?

Anaphylaxis is an adverse allergic reaction characterized by systemic clinical manifestations that appear in a subject who has been sensitized to a foreign substance upon re-exposure by any route, whether inhalation, oral or parenteral, to the same material.
Anaphylaxis is a syndrome potentially fatal, defined for the first time by Portier and Richet in 1902 as a fatal reaction to the injection of a foreign protein tolerated before during prophylactic treatment of dogs with antisera.
Anaphylaxis is a disease that affects the respiratory system and is caused by a virus.
Anaphylaxis is a type of cancer that affects the lymphatic system.