A single dose of doxycycline can lower the risk of Lyme disease when:
- The tick bite occurred where Lyme disease incidence is high or in an area where >20% of ticks are infected with Borrelia burgdorferi.
- The attached tick can be identified as an adult or nymphal blacklegged tick.
- The estimated time of attachment is ≥36 hours based on the degree of tick engorgement with blood or likely time of exposure to the tick.
- Prophylaxis can be started within 72 hours of tick removal.
- The patient has no contraindication to doxycycline.