Treatment for Tick Bite with Bullseye Rash
For a patient presenting with a bullseye (erythema migrans) rash after a tick bite in an endemic area, start oral doxycycline 100 mg twice daily for 10 days immediately without waiting for laboratory testing. 1
Diagnosis
Make the diagnosis clinically based on the appearance of the rash alone—do not order laboratory testing for typical erythema migrans. 1 The bullseye rash is pathognomonic for Lyme disease in patients with potential tick exposure in endemic areas. 2
Serological testing is not useful at this early stage of infection and will delay treatment unnecessarily. 1, 3 Antibody tests are only indicated if the rash is atypical or uncertain. 1
First-Line Antibiotic Treatment
Choose one of the following oral regimens:
- Doxycycline 100 mg twice daily for 10 days (preferred first-line) 1, 2
- Amoxicillin 500 mg three or four times daily for 14 days 1, 2
- Cefuroxime axetil 500 mg twice daily for 14 days 1, 2
The 2020 IDSA/AAN/ACR guidelines strongly recommend these shorter treatment courses (10-14 days) over longer durations, with no evidence that extended therapy improves outcomes. 1
Special Populations
For pregnant women, children under 8 years, or patients who cannot take doxycycline, use amoxicillin as the preferred alternative. 2, 4 Doxycycline is relatively contraindicated in these groups due to risks of tooth discoloration and bone development issues in children. 4, 3
If the patient cannot tolerate both doxycycline and beta-lactam antibiotics, use azithromycin for 5-10 days (preferably 7 days in the United States). 1 However, azithromycin appears to have lower efficacy than the first-line agents. 3
Expected Outcomes
- Treatment with appropriate antibiotics clears signs and symptoms in approximately 90% of patients, with a relapse rate of less than 5% at 6 months. 3
- The prognosis after treatment is excellent, and progression to later-stage Lyme disease (neurological, cardiac, or articular complications) is prevented. 3, 5
Critical Pitfalls to Avoid
Do not delay treatment while waiting for laboratory confirmation. 1 The clinical diagnosis is sufficient, and early treatment prevents serious complications.
Do not prescribe longer antibiotic courses than recommended. 1 There is no evidence that treatment beyond 10-14 days is more effective, and it increases the risk of adverse effects and antibiotic resistance.
Do not confuse this with Southern Tick-Associated Rash Illness (STARI). 1 In geographic regions where both Lyme disease and STARI are endemic (from Amblyomma americanum/lone star tick bites), distinguishing between them may not be possible clinically unless the tick has been identified. 1, 5, 6 When STARI cannot be distinguished from Lyme disease in areas endemic for both conditions, treat for Lyme disease. 1
Patient Counseling
Advise patients to drink fluids liberally with doxycycline to reduce the risk of esophageal irritation and ulceration. 4
Warn patients taking doxycycline to avoid excessive sunlight or artificial UV light and to discontinue therapy if phototoxicity (skin eruption) occurs; recommend sunscreen or sunblock. 4
Inform patients that although doxycycline absorption is not markedly influenced by food or milk, they should avoid taking it with antacids containing aluminum, calcium, or magnesium, iron-containing preparations, or bismuth subsalicylate. 4
Prevention of Future Tick Bites
- Use EPA-registered repellents (DEET, picaridin, IR3535, oil of lemon eucalyptus) on exposed skin. 2, 7
- Wear protective clothing including long-sleeved shirts, pants, socks, and closed-toe shoes in tick-infested areas. 2, 7
- Perform daily tick checks after outdoor activities. 2, 7
- Remove any attached ticks promptly using fine-tipped tweezers, grasping as close to the skin as possible and pulling upward with steady pressure. 2, 7