Single dose prophylactic treatment of a tick bite only prevents a Lyme rash

In a recent review entitled “Lyme Disease: Emergency Department Considerations,” the authors recommend using a one-time, single dose of doxycycline for the prophylactic treatment of a tick bite, [1] despite the fact that there has been only one study exploring the effectiveness of such a limited dosage. The article also neglects to mention that there are doctors who take a different approach and advise against a one-time, single dose. [2]


by Daniel J. Cameron, MD MPH

The authors cite the 2006 Infectious Diseases Society of America (IDSA) guidelines when making their recommendation that “individuals be treated with a single dose of doxycycline (4 mg/kg in children ≥8 years of age to a maximum 200 mg and 200 mg in adults)”. [1] Their recommendation applies only to patients meeting the following criteria, “(1) the attached tick is clearly identified as a nymph or adult I. scapularis; (2) the tick has been attached ≥36 hours; (3) local infection rates of ticks with B. burgdorferi is ≥20%; and (4) there are no contraindications to doxycycline.” [3]

The IDSA guidelines adopted the single, 200 mg dose of doxycycline despite the fact that three previous prophylactic antibiotic trials for a tick bite had failed.

The authors fail to mention that the IDSA single dose of doxycycline approach is based on a single study, which only found a reduction in the number of erythema migrans (EM) rashes. “A study by Nadelman et al. found that patients treated with a single dose of doxycycline developed EM manifestation at a lower rate than the placebo group (0.4% compared to 3.2%, respectively),” according to Applegren from the School of Medicine, University of Missouri.

The review also does not mention the evidence, as put forth by the International Lyme and Associated Diseases Society (ILADS), which finds that a single dose is ineffective in warding off Lyme disease. Such evidence was easily accessible via open access, peer-reviewed journals in PubMed [2], the Journal’s website, [4] and the National Guideline Clearing House. [5]

ILADS 2014 guidelines used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to conclude that the evidence for a single, 200 mg dose of doxycycline was “sparse, coming from a single study with few events, and, thus, imprecise.” [2]

There were only 9 EM rashes in the Nadelman study. Nadelman and colleagues were able to reduce the number of rashes from eight to one by prescribing a single 200 mg dose of doxycycline. The “p” value was barely significant at 0.04.

The IDSA guidelines adopted the single, 200 mg dose of doxycycline despite the fact that three previous prophylactic antibiotic trials for a tick bite had failed.

Nadelman’s study had several other limitations:

  1. It was not designed to detect Lyme disease if the rash were absent.
  2. The 6-week observation period was not designed to detect chronic or late manifestations of Lyme disease.
  3. It was not designed to assess whether a single dose of doxycycline might be effective for preventing other tick-borne illnesses such as Ehrlichia, Anaplasmosis, or Borrelia miyamotoi.

Today, patients expect to be informed of their treatment options. The recent review in the Journal of Emergency Medicine [1] would have been stronger if the authors had disclosed the evidence against using a single, 200 mg dose of doxycycline for prophylactic treatment of a tick bite.



  1. Applegren ND, Kraus CK. Lyme Disease: Emergency Department Considerations. J Emerg Med, (2017).
  2. Cameron DJ, Johnson LB, Maloney EL. Evidence assessments and guideline recommendations in Lyme disease: the clinical management of known tick bites, erythema migrans rashes and persistent disease. Expert Rev Anti Infect Ther, 1-33 (2014).
  3. Wormser GP, Dattwyler RJ, Shapiro ED et al. The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis, 43(9), 1089-1134 (2006).
  4. Cameron DJ, Johnson LB, Maloney EL. Evidence assessments and guideline recommendations in Lyme disease: the clinical management of known tick bites, erythema migrans rashes and persistent disease from Expert Review of Anti-infective Therapy 2014 at (Last accessed 1/3/16).
  5. Evidence assessments and guideline recommendations in Lyme disease: the clinical management of known tick bites, erythema migrans rashes and persistent disease. National Guideline Clearinghouse. Agency for Health Care Research and Quality. Available from: (Last accessed 10/11/15).

17 Replies to "Single dose prophylactic treatment of a tick bite only prevents a Lyme rash"

  • Tricia
    03/20/2017 (4:16 pm)

    This is exactly how my daughter at 7 became chronically ill with Lyme disease and suffered for 6 years while being bedridden. Her pediatrician assured me that a single prophylactic course of Doxy would completely prevent Lyme. Her ignorance caused my daughter to lose years of her childhood/teen years.

  • Jennifer
    04/28/2017 (12:53 pm)

    I have asked this before and I ask it again….Is there proof that the tick has to be attached for 24 hours in order for the virus to pass from the host? I would like to check this study out. I can’t seem to find anything only that “that’s just how we roll attitude”. How do they know this? What were the tests done on? When did this take place? How many times was this proven in the testing? Where’s the proof?!

    • Joyce Dahlberg
      05/24/2017 (9:46 pm)

      The # of hours is just an opinion. There has been no research done on this. It is only assuming. If you read articles many have different length. It is beyond a pandemic. It is not being acknowledged to reduce fear only. In my opinion hell will break loose very soon. Just a few days ago a 8 year old died 10 days after going to the doctors and was given another diagnosis. She died from a co infection of lyme that can be transmitted as fast as within 15 minutes. Only by drastic measures will something be done. THE TIME HAS COME TO AVOID OUTDOOR ACTIVITIES which would result in something being done because MONEY TALKS when the economy collapses due to no recreational pursuits.

    • Lorna
      05/29/2017 (7:39 pm)

      I have had Lyme – the bullseye rash, etc. – with a tick attached for less than 24 hours.

    • Jeff Levy
      07/06/2017 (9:40 pm)

      Here is a brief video that answers this question:

  • Conrad Miller
    09/23/2017 (12:29 pm)

    The truth is that as soon as the tick injects its evil brew of germs and toxins into the bitten-person’s body, these are there and the organisms will multiply vs. the individual’s immune system. Rash or no rash the borrelia, erlichia, babesiosis et al organisms will be using one’s body as a medium, symbiotic or parasitic, with there no likely 48 hour time clock threshold existing for all potential Lyme Disease victims to begin being ‘diseased’ as once proclaimed by Stony Brook Lyme Physician Dattwyler..

  • Marta O’Bosky
    04/16/2018 (3:11 am)

    I had also received 1 time dose to prevent Lyme. 2 months later came down with all the Lyme symptoms and 6 years later am still chronically ill with Lyme, Bartonella and Babesia. Years of antibiotics, herbs, supplements have done nothing. I’m in constant full body pain… they always talk about treating Lyme right away, but what about coinfections? So many people are not just infected with Lyme but also multitude of other infections. There needs to be early treatments that can treat them all.

  • jz
    08/27/2018 (7:46 pm)

    Hi – If a prophylactic antibiotic is not the right course of action, what is a better approach?

    • Dr. Daniel Cameron
      08/28/2018 (5:17 pm)

      I prophylactic antibiotic is planed, the ILADS guideline recommend the following:
      Clinicians should promptly offer antibiotic prophylaxis for known Ixodes tick bites, in which there is evidence of tick feeding, regardless of the degree of tick engorgement or the infection rate in the local tick population. The preferred regimen is 100–200 mg of doxycycline, twice daily for 20 days. Other treatment options may be appropriate on an individualized basis (see remarks below). (Recommendation, very low-quality evidence).
      You can read the guidelines at

  • Ben Wildes
    01/31/2019 (9:03 pm)

    I was given a single dose doxycycline treatment for tick bite at a walk-in clinic. Weeks later I went back because I felt like I had symptoms of Lyme. The doctor there said that they don’t do follow-up for lyme, and that I would have to find someone else. I was sick everyday for a few more weeks until I could convince another doctor to give me 20 days of doxycycline. I finally got better and I’m okay now. Do not trust the single-dose treatment.

    • Dr. Daniel Cameron
      02/01/2019 (1:00 am)

      I agree. I am sorry you had to suffer.

  • Janice
    05/08/2019 (7:39 pm)

    Today I removed an embedded female nymph deer tick which was on me 12-20 hours I think
    I took it to the local health department and the tester said it did not look engorged – I will have the test results in 3 days.

    In early 1990’s I had severe late stage Lyme with
    Neurological , arthritic and cardiac symptoms and ended up doing over 3 months of rocephin.

    Because of the previous severe problem,should I start antibiotics now? Wait 3 days? If the health department says it is not engorged is that a very
    Definitive diagnosis? They tests for Lyme and Babesiosis only and they said about 20% risk factor

    My GP had suggested taking a Westen blot and Elisa antibody test in a few weeks but could that be too late ? I live in Connecticut/land of Lyme !
    Thank you so much Dr. Cameron for helping with this devastating disease.

    • Dr. Daniel Cameron
      05/09/2019 (11:31 am)

      Thanks for sharing a few of the unresolved issues following a tick bite. The 24 to 36 hour window before infection was initially based on a mouse model and then only of the spirochete. We now know that there are tick borne pathogens that are transmitted sooner. The tick can test negative if damaged during shipping or if your blood interfered with the testing. i have to had to weigh the risks and benefit of treatment for each patient given the limited research evidence.

  • Dan
    05/11/2019 (10:46 pm)

    I noticed a bullseye shaped bruise on my leg at the end of April but never noticed anything on me or felt a bite. The mark was about an inch across. I went to a doctor and they gave me the single dose of doxycycline incase it was a tick bite. The mark never grew and faded like any normal bruise. I never had any symptoms of lyme and still dont it has been 3 weeks now. Is there a chance the mark was not tick or lyme related? It kind of felt like a bruise when touched. It had a small red mark at the center. Could something else have bitten me? Just wondering if I should have a follow up for lyme even though I have had no symptoms?

    • Dr. Daniel Cameron
      05/13/2019 (12:33 am)

      The CDC set 2 inches in diameter as a guideline. Rashes under 2 inches can come from other causes including a bruise. I am not a fan of a one time single 200 mg dose of doxycycline. I would rather follow closely or treat at least 3 weeks. You can see the rationale in ILADS guidelines at

  • J Hemingway
    05/16/2019 (12:00 pm)

    Hi Dr. Cameron, former nurse with a deer tick bite yesterday. Unfortunately, I did not recognize it as a tick and it was there at least 3-4 days and was engorged when I removed. I am in NC. Frustrating afternoon of going to urgent care and making multiple calls to practitioners and pharmacists who could not offer or offered conflicting advice. The young PA (from NJ) at urgent care subscribes to the single dose doxy. Thankfully, while frantically researching in the waiting room, I came across the ILADS site. I showed it to the PA and asked to call (to clarify if the 20 day doxy was prophylactic or once symptoms appear). He had “no time” for this. I insisted on a 20 day script and called ILADS after leaving. They could not provide info. Or clarification. I sat there with the docy in my hand and thought well…I think I should take this. My nurse friend and I decided I should do the 200 mg “loading dose” yesterday, and now will continue with 100mg BID. I feel completely alone in this and am very disappointed, yet agai , in the lack of knowledge/awareness among physicians…particularly in an endemic area such as this ?! (I am from Canada). Please, Dr. Cameron, could you confirm that I am doing the right thing at this point ? (doxy for 20 days seems like a long time…yikes) In adfition, I don’t believe they test the ticks here in NC (PA did not know, nor did he call to find out).My entomologist (retired) friend here said to forget the testing of the tick. As far as testing myself, it appears there is controversy over the accuracy of those results as well….and which type and at what stage they should be done?? Do you recommend any testing? What is to be done after the 20 day prophylaxis? Thanks so much in advance, for your time and reply. Janet H.

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