Herpes Simplex Virus (HSV) is a virus, which causes a painful skin/mucosal blistering disorder that can involve numbers areas including genitalia, lips, esophagus, and skin.  Immunohistochemistry (IHC) antibodies for HSV-1 and HSV-2 are available for testing in paraffin embedded tissue.  In general, HSV-1 infections are more common above the diaphragm, and HSV-2 are more common below the diagram.  While the availability of HSV-1 specific and HSV-2 specific antibodies for testing might suggest they are highly specific.  In the author’s experience, there is  a lot of cross reactivity between the HSV-1 and HSV-2 antibodies, and one should not consider positivity as definitively specific.

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