A word of warning about treating medical conditions via a forum: No forum can replace a doctor visit, natural or allopathic. Any suggested treatment on this or any forum should be researched by anyone that attempts to use them, preferably from multiple sources. If you have a definite diagnosis, then do the research on that disorder or treatment before starting (except for emergencies where you need immediate treatment).
Now, back to the thread. Someone with herpes type cold sores (or the other type of herpes) is not contagious between outbreaks. There are ways to keep those outbreaks to a minimum, both with medcation and with alternate treatments, and often with both. And, since the disease (at least herpes type 1) is often spread by relatives kissing during childhood, it is very common and if you already have it, you probably will not be able to get it any worse. However, you can get the type 2 version if you have type 1 (there are multiple strains). But, this would not be sufficient cause to call off a wedding, since there are ways to prevent transmission.
However, if the person was dishonest about how they got it, that would be a different problem. A person with a promiscuous past that is willing to come forth about it is much better than one who goes to great lengths to conceal it or lie about it. To me, honesty and integrity mean more than a temporary blemish that will be gone in a couple of weeks.