Jarisch-Herxheimer Reaction

The Jarisch-Herxheimer reaction (JHR) was first described in the late 1800s by Austrian dermatologist Adolf Jarisch, who observed worsening of syphilitic skin lesions following treatment with a mercurial compound. In the early 1900s, German dermatologist Karl Herxheimer independently reported a comparable clinical phenomenon. JHR is a transient inflammatory response occurring within 24 hours of initiating antibiotic therapy in patients with spirochetal infections, including syphilis, leptospirosis, Lyme disease, and relapsing fever. This reaction has also been observed in individuals receiving antibiotics for unrelated indications when an underlying spirochetal infection remains undiagnosed. Clinical features commonly include fever, chills, rigors, nausea, vomiting, headache, tachycardia, hypotension, hyperventilation, flushing, myalgia, and exacerbation of preexisting skin lesions. JHR is an acute, self-limiting condition that typically resolves without the need for targeted treatment. Accurate recognition is essential to distinguish this condition from potentially life-threatening disorders that may present with overlapping symptoms, such as severe allergic reactions and sepsis.