Q: Dear Dr. Mao,
Is a cold sore the same herpes as the sexually transmitted herpes?
A: The common virus known as herpes can cause painful blister-like lesions around the mouth and in the genitalia. Slightly different strains of herpes predominate in each of these two locations, but the infections are essentially identical. In both areas, the herpes virus has the devious habit of hiding out deep in the DNA of nerve ganglia, where it remains inactive for months or years. From time to time the virus reactivates, travels down the nerve, and starts an eruption.