I'm sorry to bother you again. This will be my final clarification. 

Contrary to Dr. Handsfield's advice, I took the full 14 day 100 mg Doxycycline.(no dairy or alcohol) and i took it with food. 

In the first 4 days every symptom disappeared and I forgot about this whole thing by the end of taking the medicine. 2 weeks after the last dose( 9,5 weeks post exposure( my neck and groin lymph nodes became painful), and in the upcoming days the same maculopapular rash on chest appeared and is on whole torso now. Its most prominent in the morning. I retested with TPHA at 10 weeks - result pending, and INSTI rapid treponemal test is negative at 10.5 weeks. 

1. Could it be that doxy did not work, and it messed up the seroconversion process? 

2. When to retest after antibiotics to be sure? 

Thank You! 

The doxycycline you took, as Dr. Handsfield told you, is highly effective for syphilis treatment and, if you had syphilis, would have  cured it.  You do not, and did not, have syphilis as your blood tests show.  If your symptoms had been due to syphilis, the tests would have been positive despite the doxycycline that you took unnecessarily.

1.  If the doxycycline had not worked, your test would have been positive.  Further testing is not needed and if you choose to not take the advice provided on the Forum, no matter how much you test, the tests will show that you did not acquire syphilis.  The symptoms you describe could have been due to any of the numerous community acquired non-STI viral illnesses that most people get from time to time.  

2.  See above- no need to retest.

Further, let me remind you that falsely positive tests do occur from time to time and the more you test, the more you are to have a falsely positive test.  EWH

The reasons why I became so worried is because I had penile lesion about 2 and half weeks after the exposure, followed later by lymph nodes pain at 5 weeks and rash which all went away on doxycycline and returned later (except for the lesion - it stayed the same and it looks like a hypopigmented scar). And that combination frightened me probably more than it should have.

Additionaly, the TPHA done at almost 10 weeks (2,5 weeks after doxy) came out negative.

I also understand your point about false positive tests. I actually experienced a false positive rapid HIV test 4 years ago, which was then, of course, overruled by other tests. That scenario probably contributed to me overtesting in this situation.

So:

1. The standard 3 month test is not needed?

2. If the antibiotic failure happened, how long does it usualy take for symptoms to rebound?

3. In clinical practice, are true treatment failures rare with doxycycline vs penicilin? 

Thank You.

1.  Correct

2.  In person who failed therapy, typically the only evidence of treatment failure is a positive test. Once again, I will urge you to believe your tests.

3.  Yes

EWH

Thank You for answering. 

1.  The same sorts of blood tests have been used for over 75 years.  Recommendations for interpretation are often out of date and do not mesh with what is observed clinically.     Antibodies to anything that elicits an immune response is usually present within two weeks of infection and always within 4 weeks;  Whomever told you that it takes 16 weeks for accurate test results  is misinformed..

2.  Yes, see my comment above.

3.  I considered all of the information you provided in my response and used my experience as an advisor to the CDC on syphilis for over 40 years, my more than 40 syphilis research papers and my multiple textbook chapters in my response.  My assessment is not going to change.

I hope that the information I have provided is helpful.  End of thread.  EWH