Herxheimer Reaction in Lyme Disease: What Happens After Treatment Starts
Symptoms may worsen after treatment begins
This reaction is temporary but concerning
Recognizing it prevents misdiagnosis
Herxheimer reaction Lyme disease refers to a short-term worsening of symptoms after starting antibiotic therapy. This reaction can be alarming but is typically self-limited.
A Jarisch-Herxheimer reaction (JHR) is an inflammatory response first described in syphilis but also seen in other spirochetal infections, including Lyme disease.
Symptoms often overlap with those described in the Lyme disease symptoms guide, making it difficult to distinguish between disease progression and treatment response.
What Is a Herxheimer Reaction?
Herxheimer reactions typically develop within several hours after starting antimicrobial therapy.
Common features include:
- Fever
- Chills
- Tachycardia
- Temporary worsening of symptoms
Although usually short-lived, the reaction can be clinically concerning—especially in vulnerable populations.
Case: Neonatal Lyme Disease
Lyme disease in neonates is uncommon but can occur when a tick bite is documented.
In this case, a 21-day-old infant presented with decreased activity, poor feeding, and abdominal distension.
An engorged tick had been removed five days earlier, and an erythema migrans rash was noted at the site—supporting early Lyme disease.
Intravenous ceftriaxone was started based on clinical diagnosis.
Development of the Herxheimer Reaction
Within two hours of starting antibiotics, the infant developed:
- Fever
- Tachycardia
- Clinical signs consistent with a Herxheimer reaction
The infant was monitored closely, and symptoms resolved as treatment continued.
Laboratory testing for Lyme disease was negative, which can occur early in infection or in neonates with immature immune responses.
Why This Reaction Occurs
The exact mechanism is not fully understood.
Current evidence suggests that rapid destruction of spirochetes triggers an inflammatory response.
This process involves cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukins, leading to systemic symptoms.
Understanding this process helps explain why symptoms may temporarily worsen after treatment begins.
Why Recognition Matters
A Herxheimer reaction can be mistaken for clinical deterioration or treatment failure.
When symptoms worsen shortly after starting antibiotics, clinicians should consider a Herxheimer reaction rather than stopping treatment prematurely.
This distinction is important in avoiding unnecessary changes in therapy—a pattern sometimes seen in Lyme disease misdiagnosis.
Clinical Perspective
Herxheimer reactions highlight the complexity of treating Lyme disease.
Symptoms may worsen before they improve, particularly in early or disseminated infection.
Recognizing this pattern allows clinicians to continue appropriate therapy while providing supportive care.
Video: Understanding the Herxheimer Reaction
References
- Insights into the Pathophysiology of the Jarisch-Herxheimer Reaction. Infectious Disease Review. 2020.
- Lyme Disease in a Neonate Complicated by the Jarisch-Herxheimer Reaction. Pediatric Infectious Disease Journal. 2020.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
