anaphylactic (adj.)

"of or pertaining to a severe allergic reaction," 1905, with -ic + medical Latin noun anaphylaxis "exaggerated susceptibility," from Greek an- "without" (see an- (1)) + phylaxis "protection," from phylax "guardian, watcher, protector," a word of unknown origin. Compare prophylactic. Anaphylactic shock is attested by 1916.