How could docs take a sample of herpes sore without blood?

A viral culture: sample and be obtained by swabbing an open,active lesion.

Swab: If you have a sore, a swab can be used to send off for testing. This is almost as good as testing blood for antibodies and has the advantage of telling you where the virus is since the blood test only tells you that your body has seen the virus but tells you nothing about the location of the infection. HSV type one and type two can both cause both fever blisters and genital sores.