How long after a cold sore can i perform oral on my partner ?

Oral herpes: It should be completely healed -- i.e. no open sores and any scabs should have fallen away on their own. Usually this means at least a week and often up to 2 weeks after onset of an outbreak. The same is true for kissing anyone -- not just oral sex. Your partner could consider a blood test for HSV. Up to half of all people are positive for HSV1. If so, he is immune and can't catch it from you.