Herpes

Oral or genital herpes infections may be caused by Herpes Simplex Virus I (HSVI) or Herpes Simplex Virus II (HSVII). Either virus may infect the oral or genital regions. Blood testing for these viruses is done by measuring antibodies in the blood.

Most common contact with these viruses occurs in childhood usually from a known or unknown oral infection.
 

In fact, over 50% of adults show some evidence of some HSV infection. Antibodies are most useful when they are entirely negative... suggesting no evidence of any HSV infection. Blood antibodies may also be useful by studying both IgM and IgG type antibodies.

Many believe that a positive IgM antibody suggests active infection. If the IgG antibodies are measured during and then (a few weeks) after a suspected infection, a substantial difference (4-fold or greater) suggests HSV infection.

As always blood tests should be interpreted along with a full clinical evaluation by a qualified physician.