- During an outbreak:
Your healthcare provider will look at the sores and see if they seem typical of a herpes outbreak. If they are, your provider may swab the sores to see if they contain virus. However, this swab test is not always accurate and has a high risk of false negatives. An outbreak that looks like herpes, but that comes back with a negative test for virus, may still be a herpes infection. Testing a swab for virus is most useful in the first 48 hours of a first outbreak. After that, and during recurrent outbreaks, it becomes much less accurate.
Herpes outbreaks usually appear as one or more blisters that then break open to become sores.
- Not during an outbreak:
Although there are commercial blood tests for herpes that looks for antibodies against HSV1 and HSV2, they do not always give conclusive results. There are type-specific blood tests that are more accurate, but these may be more difficult to find. An excellent overview of Herpes testing, that links to a review of current blood tests, can be found here