The most common reason that people develop cold sores on their mouths is due to becoming infected with HSV-1. (4) HSV-1 usually causes cold sore breakouts around the lips or mouth, or what some people describe as “fever blisters.” Someone can become infected with HSV-1 starting as a child, and then the virus can lay dormant in the body until the immune system is weakened, at which point symptoms can surface.

These herpes viruses enter the body through small cuts, abrasions, or breaks in the skin or mucous membranes. The incubation period for herpes simplex infections is about three to six days. Transmission (spread) of the virus is person to person and more likely to occur if blisters or lesions are present. The majority enter after an uninfected person has direct contact with someone carrying the virus (either with or without noticeable lesions). Simply touching an infected person is often the way children get exposed. Adolescents and adults frequently get exposed by skin contact but may get their first exposure by kissing or sexual contact (oral and/or genital contact), especially for HSV-2. Statistical studies suggest that about 80%-90% of people in the U.S. have been exposed to HSV-1 and about 30% have been exposed to HSV-2. Usually, the contagious period continues until lesions heal. Some people (estimated from 30%-50%) occasionally shed herpes virus while having few or no associated symptoms or signs.
The herpes simplex virus is probably the most well-known virus of the herpes family, and it is just as contagious. Herpes simplex infects epithelial cells and remains latent in neurons. HSV-1 causes recurrent oropharyngeal lesions, commonly known as “fever blisters" or "cold sores.” It is also the primary cause of sporadic encephalitis (inflammation of the brain), gingivostomatitis (inflammation of the gums and mucous lining of the mouth), and keratoconjunctivitis (severe dryness of the eye that involves the cornea) and dendritic corneal ulcers (also called HSV keratitis) in which the cornea becomes affected by herpetic lesions that look like the dendrites of neurons in the brain.

The annual incidence in Canada of genital herpes due to HSV-1 and HSV-2 infection is not known (for a review of HSV-1/HSV-2 prevalence and incidence studies worldwide, see Smith and Robinson 2002). As many as one in seven Canadians aged 14 to 59 may be infected with herpes simplex type 2 virus[85] and more than 90 per cent of them may be unaware of their status, a new study suggests.[86] In the United States, it is estimated that about 1,640,000 HSV-2 seroconversions occur yearly (730,000 men and 910,000 women, or 8.4 per 1,000 persons).[87]
There’s quite a variety, in short. And while genital herpes certainly can and does cause these signs of infection literally on the genitals (the penis or the vulva) it also can produce signs of infection nearby. Herpes sores on or between the buttocks are common (and sometimes slow to heal), as are lesions on the thigh. Herpes can bring about what feels like a tiny fissure around the anus, something easily confused with hemorrhoids. So remember: recurring signs and symptoms in the genital or anal area could well be herpes lesions.
There’s herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). “HSV-1 and HSV-2 are different but closely related viruses,” says Dr. Christine Johnston, MPH, who is the Associate Medical Director of the Virology Research Clinic at the University of Washington. Johnston explains that both are transmitted through close mucosal or skin contact with infected secretions. HSV-1 primarily causes oral outbreaks, also known as cold sores, and HSV-2 usually causes genital outbreaks. But HSV-1 can also cause genital outbreaks through oral-to-genital contact, according to the CDC. According to Johnston, genital HSV-1 is less likely to recur than HSV-2, and there’s less asymptomatic shedding (transmitting the virus without realizing it) with HSV-1 than with HSV-2.
The herpes virus can be shed from an infected person even when there are no lesions visible. So caution is important. Some may wish to take the daily prophylactic oral drug Valtrex (an antiviral oral medication) to help cut down on shedding. Herpes can also be transmitted on any skin: fingers, lips, etc. Depending on sexual practices, herpes simplex can be transferred to genitals and or buttocks from the lips of someone who has fever blisters. Honesty between partners is very important so these issues can be discussed openly.
Stage 3 -- Recurrence: When people encounter certain stresses (also termed triggers), emotional or physical, the virus may reactivate and cause new sores and symptoms. The following factors may contribute to or trigger recurrence: stress, illness, ultraviolet light (UV rays including sunshine), fever, fatigue, hormonal changes (for example, menstruation), immune depression, and trauma to a site or a nerve region where previous HSV infection occurred.
Herpes virus type 1 (HSV-1) is the cause of cold sores or fever blisters around the mouth. Usually, the sores or blisters can show up on the outside of the mouth or on the lips. But sometimes, they can be inside the mouth, on the face, nose, cheeks or fingers. HSV-1 can also lead to infection of the genitals, called genital herpes. This occurs when you have a cold sore and perform oral sex on another person. HSV-1 infections are highly contagious. Apart from oral-genital contact, they can be spread through skin-to-skin contact. If you come into contact with a person or a thing that carries HSV-1, you will be likely to get it, too. Often, people get HSV-1 from kissing someone with a cold sore or when they share eating utensils, razors, or towels.

The frequency and severity of recurrent outbreaks vary greatly between people. Some individuals' outbreaks can be quite debilitating, with large, painful lesions persisting for several weeks, while others experience only minor itching or burning for a few days. Some evidence indicates genetics play a role in the frequency of cold sore outbreaks. An area of human chromosome 21 that includes six genes has been linked to frequent oral herpes outbreaks. An immunity to the virus is built over time. Most infected individuals experience fewer outbreaks and outbreak symptoms often become less severe. After several years, some people become perpetually asymptomatic and no longer experience outbreaks, though they may still be contagious to others. Immunocompromised individuals may experience longer, more frequent, and more severe episodes. Antiviral medication has been proven to shorten the frequency and duration of outbreaks.[79] Outbreaks may occur at the original site of the infection or in proximity to nerve endings that reach out from the infected ganglia. In the case of a genital infection, sores can appear at the original site of infection or near the base of the spine, the buttocks, or the back of the thighs. HSV-2-infected individuals are at higher risk for acquiring HIV when practicing unprotected sex with HIV-positive persons, in particular during an outbreak with active lesions.[80]


According to Melissa King, a psychotherapist who runs a support group for women with herpes in New York City, when someone finds out they’ve gotten herpes from a partner, there’s often immediately an assumption that the partner knew that they had it and lied, or that they were cheating. “But the reality is that in a lot of cases, people don’t know that they have it,” King tells BuzzFeed.
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