Me too, but can not answer the question - only give a data point: I have the impression that the virus stays dormant at the nerve root at spinal cord for long periods (not sure this is correct) then migrates along the nerve to the same body surface site to make the sore. That is consistent with my 20 or so years of experience. My sore is always on lower right lip, often near the corner. Last time, however it made it to near middle of lower lip. Hardly any pain. It just seems that the surface skin falls apart with minor lymphatic fluid loss. It only happens once or twice each year. I still have the tiny bottle of 20% Benzocaine (KANKA is the brand name) from 20+ years ago! When applied with the glass ball-tipped stick, an air tight film rapidly forms in minutes. If done in first day or so, sore is gone three days later. If applied after 3 or more days, it takes a week to cure. Bottle is more than half full still – It will very likely survive me but should be discarded, not used by anyone else.