Hello doctor, Last week I woke up with what appeared to be three to four tiny blisters on my upper left lip, outside of the mouth, not inside. I recently had a baby and have not left the house except to go to a dental appointment one week before developing these small blisters. I went to the doctor a few hours after finding the blisters, and she ran an Ig blood test which came back negative. I also had an HSV 1 and HSV 2 test done before seven months before giving birth that came back negative. So I know I was not a carrier of the virus. After seeing what could be the beginning of primary infection, my doctor prophylactically put me on a dose of Valtrex. Three days before we did a culture swab test which came back today as negative. My question is, are there any possible ailments that would closely mirror a cold sore? I understand that if my primary infection was only two weeks ago, it is possible that it would be undetectable in the bloodstream but I was surprised that the culture swab came back negative as well. Could this be because of the use of Abreva earlier in the day? The blisters never leaked much fluid, so it was quite hard to get a great sample on the swab. After a few days, the blisters never turned into an open sore, just slowly dried and tingled a little. At this point, they appear to be gone entirely. There was never any pain associated with the sore.
Hello. 1. There can be other skin diseases which mimic HSV 1 infection on lips, but still, it is quite characteristic clinically, things which can sometimes look like are paederus dermatitis, hand foot, and mouth disease, but it is seen usually in children and blisters elsewhere are also present. Candida can be there, but it rarely presents as blisters in adults. 2. To conclude the appearance is quite characteristic and your description of vesicles and their evolution looks like HSV. 3. The serology can take up to a month (average 2 to 4 weeks) to become positive after primary infection, HSV IgM will be detectable at that time in serum. So it might be one of the reasons for that. 4. For culture the sensitivity overall is 50 percent, that is 50 out 100 patients culture will grow the virus. Although in primary syphilis sensitivity is up to 80 percent. 5. When lesions start to heal it is difficult for a culture to get a positive result. Also, fluid will be required for it to be positive. Either fluid from blisters or erosions whatever is present. It will not come positive if the sample is taken from the surface of the vesicle. 6. My advice is to repeat serology after 3 to 4 weeks once again, and even if it is positive, you do not need to get frightened so much as HSV 1 serology is usually seen in 50 to 75 percent cases. It does not mean it will come back again, though being a carrier chance of spread is there somewhat.