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.

If abstinence is not possible, using a sexual barrier (such as a condom or dental dam) can reduce the likelihood of transmission, although there is still a risk that these methods will not be sufficient to prevent the spread of the virus. It’s also a good idea to keep a visual reminder of your infection at hand to avoid any accidental food or beverage sharing.

Herpes virus type 4 is also called Epstein-Barr virus. It typically causes infectious mononucleosis, a “kissing” disease. Symptoms include skin rash, fever, sore throat and swollen lymph glands. The virus can be involved in cancers like nasopharyngeal cancer. Herpes virus type 4 is contagious through bodily fluids, including saliva. Kissing, coughing, sneezing, or sharing utensils can make the infection spread.
It should not be confused with conditions caused by other viruses in the herpesviridae family such as herpes zoster, which is caused by varicella zoster virus. The differential diagnosis includes hand, foot and mouth disease due to similar lesions on the skin. Lymphangioma circumscriptum and dermatitis herpetiformis may also have a similar appearance.

Although herpes treatment is helpful, there is no cure. However, in most cases, outbreaks become fewer, less painful, and weaker over the course of a few years. If you have herpes, you can take certain medications to help manage the infection. Using herpes treatments is usually very effective in speeding up the healing of sores and preventing them from returning frequently.


HSV asymptomatic shedding occurs at some time in most individuals infected with herpes. It can occur more than a week before or after a symptomatic recurrence in 50% of cases.[33] Virus enters into susceptible cells by entry receptors[34] such as nectin-1, HVEM and 3-O sulfated heparan sulfate.[35] Infected people who show no visible symptoms may still shed and transmit viruses through their skin; asymptomatic shedding may represent the most common form of HSV-2 transmission.[33] Asymptomatic shedding is more frequent within the first 12 months of acquiring HSV. Concurrent infection with HIV increases the frequency and duration of asymptomatic shedding.[36] Some individuals may have much lower patterns of shedding, but evidence supporting this is not fully verified; no significant differences are seen in the frequency of asymptomatic shedding when comparing persons with one to 12 annual recurrences to those with no recurrences.[33]
While some people realize that they have genital herpes, many do not. It is estimated that one in five persons in the United States has genital herpes; however, as many as 90 percent are unaware that they have the virus. This is because many people have very mild symptoms that go unrecognized or are mistaken for another condition or no symptoms at all.
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.
A doctor will base a presumptive diagnosis on information provided by the patient and on the physical examination. The characteristic appearance of the herpes sores leaves little doubt about the diagnosis, so the typical appearance of the sores is key to the diagnosis. This appearance helps distinguish oral herpes from oral thrush, shingles, gonorrhea, and syphilis. In addition, chapped or sunburned lips can resemble oral herpes, but the tissue stain (Tzanck smear, see below) shows no virus-induced cell changes. Further testing is usually not necessary but is sometimes done.
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