From Wikipedia: An oral ulcer (from Latin ulcus) is the name for the appearance of an open sore inside the mouth caused by a break in the mucous membrane or the epithelium on the lips or surrounding the mouth. The types of oral ulcers are diverse, with a multitude of associated causes including: physical or chemical trauma, infection from microorganisms or viruses, medical conditions or medications, cancerous and sometimes nonspecific processes. Once formed, the ulcer may be maintained by inflammation and/or secondary infection. Two common oral ulcer types are aphthous ulcers (canker sores) and cold sores. Cold sores are caused by the herpes simplex virus. So since there are 2 types it is not 100% guaranteed that you have the herpes strain. I would get it tested to see, and i am rooting for you that it is not the case.

ALL cold sores on your lip are caused by one of the two herpes viruses, hsv-1 or hsv-2. MOST, about 95%, of cold sores, are caused by the virus hsv-1, while hsv-2 is found more often on the genitals. A 'cold sore' or a fever blister' is just an old-fashioned name for an outbreak of oral herpes on your mouth. The herpes virus stays dormant in the nerves of your face once your mouth becomes infected. Outbreaks can be triggered by sun exposure or stress, or anything that affects your immune system such as a cold or a fever - hence the old names because that was when they commonly occurred. If you have ORAL herpes, which is what a cold sore is, then you do not count as having an std, because it is your mouth is infected not your genitals. Oral herpes is extremely common - around 50% of high school students already have it, and by the time you reach 50 there is a 95% chance of having caught hsv-1. Oral herpes is often caught as a baby or small child, through being kissed by an adult who carries the virus. By adulthood, four fifths of people carrying the virus never get symptoms and are unaware that they have it. You can still just get an outbreak out of the blue. In your case, you may have recently caught the virus from someone else with it kissing you (they could have passed in on to you without showing symptoms) or you could have been carrying it since childhood. As for your std screen, be aware that the vast majority of std screens do not test for herpes. The herpes test is a special-request blood test. If you have oral herpes, then yes, it would show up on a herpes blood test as positivity for hsv-1, but not if you had caught it in the last 3-6 months because it takes time for the presence of the virus to show in your blood. What you need to know is that although YOU don't have an std, you only have oral herpes, you CAN give any partner the std herpes if you give them unprotected oral sex (though this is very unlikely if they also have oral herpes hsv-1 because they will produce antibodies to the virus). In fact, 70% of new genital herpes infections are hsv-1 caught through receiving oral sex from a partner with a history of oral herpes. Oral herpes, aka cold sores, is infectious about 18% of the time on average, although it varies fro person to person. You DON'T have to have a cold sore, or be getting one, to infect someone else. The most common way to pass it on is when you have no symptoms. There is a common misconception that oral herpes is only infectious when you have a cold sore, while genital herpes can be infectious at any time. This is untrue - oral herpes can also be infectious at any time. Be aware and tell your partners of the risk. I have genital hsv-1. My longterm boyfriend has got cold sores, but he trained as a nurse and was taught he could not infect me genitally when he did not have a cold sore. So he used to give me oral sex when he didn't have a cold sore and thought it was safe. Then I caught genital herpes one time when he had NO sore, and the doctor explained to me that it can actually be passed from the mouth with no symptoms. Strangely enough, my sister also caught genital hsv-1 this way, and her husband hadn't had a cold sore since childhood. You see neither of our parents got cold sores so we had never caught the virus orally. Catching genital herpes this way is getting more common than the genital-to-genital way. Hsv-1 causes a milder form of genital herpes, but it is still genital herpes and someone who catches it has to deal with that stigma for the rest of their life. If you want to know of you have oral herpes, ask for a herpes specific blood test, but wait until at least three months after your first cold sore.