Jarisch–Herxheimer reaction

A transient inflammatory response that can follow antimicrobial treatment of spirochetal infections, often causing fever, chills, and worsening symptoms.

Tumor necrosis factor: A signaling protein that coordinates inflammation and can induce fever. Its rise during the reaction helps explain the acute fever and systemic inflammation.
Syphilis: A sexually transmitted infection caused by the bacterium Treponema pallidum. This is the infection most commonly associated with the reaction after antibiotic treatment.
Adolf Jarisch: An Austrian dermatologist who described treatment-associated reactions in patients with syphilis. His observations supplied the first part of the reaction’s name.
Endotoxin shock: A severe circulatory and inflammatory response caused by bacterial endotoxin entering the bloodstream. The reaction is usually self-limited and should not be equated with life-threatening endotoxin shock.
Interleukin 6: An inflammatory cytokine involved in fever, immune regulation, and acute-phase responses. Elevated levels are associated with the reaction’s fever and inflammatory symptoms.
Lyme disease: An infection caused by Borrelia bacteria and transmitted by certain ticks. Treatment can provoke a similar reaction, particularly in early infection.
Karl Herxheimer: A German dermatologist who reported inflammatory worsening after treating syphilis. His clinical reports helped establish the reaction as a distinct treatment phenomenon.
Drug fever: A fever caused by a medication, often through an immune or pharmacologic effect. Drug fever is an adverse drug response, whereas this reaction follows treatment of infection.
Lipopolysaccharide: A bacterial outer-membrane molecule that can trigger strong inflammation in Gram-negative infections. It is often invoked by analogy, but spirochetes do not have lipopolysaccharide.
Relapsing fever: A tick- or louse-borne infection marked by recurrent episodes of fever, usually caused by Borrelia bacteria. Antibiotic treatment can trigger the reaction in this spirochetal infection.

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BenzylpenicillinRelated: It may occur after benzylpenicillin rapidly kills organisms in infections such as syphilis.