Some information for you. Herpes is a virus. Once you contract it, you have it for life. When your immune system is weak you can have an outbreak. the outbreak manifest as little vesicles that contain the virus the vesicles break and release a liquid ( this is the virus reproducing itself). Contact with this liquid or the vesicles is very contagious, the broken vesicles leave an open wound than will eventually heal. The virus can't penetrate the skin defenses, so it invades your body through areas where you don't have skin ( mucous tissues like lips and mouth, genitals, eyes, open wounds on skin etc ) There are 2 types of Herpes, Type I appears on the mouth, Type II appears on the genitals. It is in fact almost the same virus, only chaning in terminology according the region where they appear, they are on the same family as Varicella and Zoster viruses. When people have an outbreak it is clearly visible, so it it easy to avoid infection, during that time, and usually if you have vesicles or open wounds on your genitals, you would't have sex during outbreaks. The problems are that the virus is contagious also just before the outbreak. so no visible outbreak yet but the virus is already on the mucous tissues ( genitals, lips etc ), and also many women have the outbreaks inside their vaginas, so they don't even know they are having it. Many think they are just some urinal infection or menstruation pains. Many people who have the virus, contract it usually when they are babies and were kissed by someone with an outbreak, others through sex on those periods when the virus is active. Now. From a medical point of view, the herpes is very benign, it is no different to any other flu. Most people have seldom outbreaks, some have them once a year or every some years, some have it every month. It really depends on how strong is your immune system. Usually the outbreak last some days ( 2 or 3 ) and the wound healing lasts maybe a week, usually it leaves no scar. If you think about it, the common flu works in the same way. You contract it, you carry the virus for life, when your immune system is weak you get a flu, your nose and throat become immflamated, and red because you have the virus active there ( mucous tissues again), and spread it around when you sneaze. Your immune system controls the virus and its gone in some days ( 3 or 4 maybe ). You are only contagious when you are having the flu, not otherwise. The Herpes viruses work in exactly identical way. The only difference is the stigma people attribute to it, because it appears on the genitals and is sexually transmitted ( mucous tissues in contact ). The only real danger this virus presents is when it attacks an immunodefficient patient ( someone with AIDs for example ) or to a baby during the delivery ( the baby hasn't enough defenses to fight the virus at the moment of birth ), in those cases it could attact the central nervous system and lead to death. But the cases are very rare. Dealbreaker ? It depends, as many people said, if it is for a one night stand, and you "know" you don't have it, you better pass. Many people have it but don't know anyway If it is for a relationship with a worthy person, why? Would you dump or pass on a good girl because she has a common flu once in a while ?