Welcome to the Forum Let's deal with the good news first- glad to hear that you do not have syphilis and to endorse the fact that your doctor did everything with relationship to your care precisely right.
As for what the rash might have been, this is difficult to say and might be better addresses. There are no STDs which would account for a rash such as the one you describe. If the rash has gone away, you may never know. Rashes such as the one you describe can be the result of a wide variety of viral infections as well as eczematous dermatitis. If the rash is still present, you may also want to either ask your own doctor, dermatologist or to ask this question on the MedHelp Dermatology expert site.
Sorry I don't have more to offer. Take care. EWH
The rash of syphilis can be highly variable however everyone who has a rash has a positve blood test. Your blood test was negative, therefore you do not have syphilis. In addition and as a "just in case", the treatement you received (two shots of penicillin) would cure syphilis if that were what was going on. this rash is due to something else (other than an STD). You do not need to be concerned about syphilis. EWH.
Thank you for your quick reply. I take it from what you said that the test results at 10 weeks are totally reliable and I do not need to be retested? Also it sounds as if you don't think the rash I had is typical of a syhpilis rash. I don't want to put words in your mouth but is that what you are saying? I still have the rash although it seems to be fading very slowly. If it doesn't go away soon I will follow up with a dermatologist. Thanks again.