It's not 100% protection but it's pretty darn good protection. It's still a good idea to err on the side of caution a little - for instance if both partners have hsv1 orally, I don't recommend going down on your partner when you have an active cold sore - for both your partner's protection and your own ( a cold sore is an active lesion into the body for germs and the normal flora in the genital area, isn't always so normal on other body parts ). Same as if one partner has genital hsv1 and the other has oral hsv1, I don't recommend having sex when the partner with genital herpes has active lesions present. Hope that makes sense?
grace
I saw one of Dr. HHH forum, he mentioned that if you have HSV 1, you will be immune of getting it in another location. He also mentioned that you will never get the infection in another location once you have HSV 1 antibody.
What is your thought of the above statement? How true is that?
Usually just avoiding sex during obvious genital lesions is all it takes. You both have significant protection against getting it in the other area .
grace