Herxheimer Reaction in a Newborn With Lyme Disease

Antibiotics can trigger a Herxheimer reaction.
A newborn developed fever and tachycardia after treatment.
Clinicians diagnosed neonatal Lyme disease.

Jarisch-Herxheimer reactions have been reported in adults and children treated for Lyme disease, but published neonatal cases remain rare.

In 2020, investigators described a 13-year-old boy with Lyme arthritis who developed worsening pain, fever, and myalgias during doxycycline treatment.

You can read more about that case here: Herxheimer reaction in a 13-year-old boy with Lyme disease.

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Newborn With Lyme Disease Developed Herxheimer Reaction

In their article “Lyme disease in a neonate complicated by the Jarisch–Herxheimer reaction,” Prodanuk and colleagues describe the case of a 21-day-old infant admitted with decreased activity, poor feeding, and abdominal distension.

The parents had removed an engorged tick from the infant’s forearm 5 days earlier.

An erythema migrans rash was present at the site of the tick bite.

“Given the erythema migrans lesion at the site from which the engorged tick was removed, we made a presumptive diagnosis of Lyme disease and administered IV ceftriaxone,” the authors wrote.

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Symptoms of a Jarisch-Herxheimer Reaction

Two hours after antibiotic treatment began, the infant developed fever, tachycardia, and worsening symptoms consistent with a Jarisch-Herxheimer reaction.

A Jarisch-Herxheimer reaction — often called a “Herx” reaction by patients — is a temporary inflammatory response that can occur shortly after antibiotics are started for Lyme disease.

Initial laboratory testing for Lyme disease was negative.

Clinicians should “be aware of the possibility of the Jarisch-Herxheimer reaction during the initial phase of treatment,” the authors warned.

Symptoms associated with Jarisch-Herxheimer reactions may include fever, chills, hypotension, tachycardia, worsening pain, muscle aches, headache, nausea, worsening of existing symptoms, or development of new symptoms.

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Why Herxheimer Reactions Matter in Neonatal Lyme Disease

The authors noted that newborns with early localized Lyme disease may be at increased risk for disseminated infection.

“Given the limited data for neonates and the possible predisposition of this population to disseminated Lyme disease, clinicians should strongly consider administering IV antibiotics to target Lyme disease,” the authors suggested.

The exact mechanism behind Jarisch-Herxheimer reactions remains unclear.

“At first, the role of an endotoxin in the development of JHR was suggested, but later experimental studies showed that spirochetes do not have biologically active endotoxins,” the authors explained.

This case highlights how difficult Lyme disease can be to evaluate in newborns, especially when laboratory testing is negative early in the course of illness.

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FAQ: Herxheimer Reaction and Lyme Disease

What is a Jarisch-Herxheimer reaction?

A Jarisch-Herxheimer reaction is an inflammatory response that can occur shortly after antibiotic treatment begins for infections caused by spirochetes, including Lyme disease.

What symptoms can occur during a Herxheimer reaction?

Symptoms may include fever, chills, rapid heart rate, worsening pain, muscle aches, headache, fatigue, or temporary worsening of existing symptoms.

Can infants develop a Herxheimer reaction from Lyme disease treatment?

Yes. Although uncommon, this case demonstrates that newborns treated for Lyme disease may develop a Jarisch-Herxheimer reaction shortly after antibiotics are started.

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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