Can someone please reassure me that a cold sore is not contagious BEFORE it makes an appearance? I know that they can be passed on through oral sex,and I am always very conscientious of this fact,I won't give DP a BJ if I have one and always make sure it is 100% gone before I do. But I developed a cold sore yesterday evening,which was about 30 hours after giving DP a BJ. This has never happened before,and now I'm stressing that it may have been 'lurking' and I've given it to him!