Arthus reaction /ärto̅o̅s″/ [Nicholas M. Arthus, French physiologist, 1862–1945] , a rare, severe, immediate nonatopic hypersensitivity reaction to the injection of a foreign substance, that usually is not irritating but in certain individuals is antigenic. The reaction is thought to involve the formation of an antigen-antibody complex that activates complement. Acute local inflammation, usually in the skin and marked by edema, hemorrhage, and necrosis, occurs at the site of injection. Also called Arthus phenomenon. See also serum sickness.
