[1] Signs and symptoms include fever, chills, shivers, feeling sick, headache, fast heart beat, low blood pressure, breathing fast, flushing of skin, muscle aches, and worsening of skin lesions.

It usually manifests in 1–3 hours after the first dose of antibiotics as fever, chills, rigor, hypotension, headache, tachycardia, hyperventilation, vasodilation with flushing, myalgia (muscle pain), exacerbation of skin lesions and anxiety.

[4] There have been case reports of the Jarisch–Herxheimer reaction accompanying treatment of other infections, including Q fever, bartonellosis, brucellosis, trichinellosis, and African trypanosomiasis.

[3] The Herxheimer reaction has shown an increase in inflammatory cytokines during the period of exacerbation, including tumor necrosis factor alpha, interleukin-6 and interleukin-8.

Patients must be closely monitored for the potential complications (collapse and shock) and may require IV fluids to maintain adequate blood pressure.