Doxycycline for Lyme disease prevention is often recommended as a single dose after a tick bite. But does this approach actually work — especially in children? A recent article by Carriveau and colleagues in Nursing Clinics of North America raises important questions about the evidence behind this recommendation.¹

The Evidence Behind Doxycycline for Lyme Disease Prevention

The authors reference a small study to support their recommendation for using a single doxycycline dosage. The study, conducted by Drs. Fish, Nadelman and Wormser, however, involved adults, not children.²
More importantly, the study was designed to demonstrate that a single dose of doxycycline could prevent an erythema migrans (EM) rash. It did not evaluate efficacy in preventing other acute or chronic manifestations of Lyme disease.

Does This Approach Work in Children?

“Recommendations for oral prophylaxis have yet to be tested on children, and have been extrapolated to include children older than 8,” write Carriveau and colleagues.
Nevertheless, in their article, Carriveau et al. make this recommendation for children over the age of 8: “In the pediatric patient 8 years or older, a single 4-mg/kg dose of doxycycline is recommended, up to 200 mg.”
For younger children, the authors take a different stance: “At this time, prophylactic treatment for children younger than 8 is not recommended.”

What the Nadelman Study Actually Showed

The Nadelman study found that a placebo group (who did not receive antibiotics) developed 8 erythema migrans (EM) rashes after a tick bite. In comparison, the group which received a single dose of doxycycline developed only 1 EM rash.
[bctt tweet=”A single dose of doxycycline only prevents a rash, not other acute or chronic Lyme disease symptoms.” username=”DrDanielCameron”]
These findings suggest that a single dose of doxycycline may prevent an EM rash but there’s no evidence indicating that it is effective in preventing other manifestations, including heart block, Bell’s palsy, Lyme arthritis, and neurologic Lyme disease.

Why ILADS Questions Single-Dose Prophylaxis

In fact, in their 2014 evidence-based guidelines, the International Lyme and Associated Diseases Society (ILADS) advises against using a single dose of doxycycline for a tick bite in adults.³
The ILADS guidelines recommend a three-week course of antibiotics with follow-up if treating prophylactically.
READ MORE: An in-depth discussion of ILADS’ reasons for advising against using a single dose of doxycycline to prevent Lyme disease.
READ MORE: Pro’s and Con’s of doxycycline for children with Lyme disease

The Bottom Line on Doxycycline for Lyme Disease Prevention

The evidence supporting single-dose doxycycline for Lyme disease prevention is limited. The original study only measured prevention of an EM rash — not heart block, Bell’s palsy, arthritis, or neurologic involvement. And it was conducted in adults, not children.
Before relying on a single dose, patients and clinicians should weigh the risks of undertreating a potentially serious infection.
For a complete guide to preventing Lyme disease from becoming chronic, see Preventing Chronic Lyme Disease: Why Early Care Matters.
Editor’s note: For transparency purposes, I am one of the authors of the ILADS evidence-based guidelines.