Viral culture of blister fluid from lesion positive for herpes simplex virus. Herpes simplex virus may grow within 2-3 days. If this test is positive, it is almost 100% accurate, especially if the fluid is from an initial blister rather than a recurrent blister. Since viruses can be hard to grow, it is often negative, even when herpes is present.
Detection of the herpes simplex virus DNA by PCR from the blister fluid. The blister fluid contains human cells and virus particles. PCR is a technique that detects small amounts of DNA and could tell you if the herpes virus was present in the blister.
Tzanck test of skin lesion may show results consistent with herpes virus infection. This test involves staining human cells within the blister fluid with a dye. If the cells from the fluid contain viral particles, they become visible. However, the test cannot determine which strain of virus is present in the blister.
Recently developed antibody tests can determine if a person has HSV-1 or HSV-2, as well as if they were exposed to either of these strains in the past (IgG test) or was just recently exposed to one of them (IgM test).