Cold sores, also known as fever blisters, are clear, fluid-filled blisters that occur on the lips and around the mouth. Cold sores may appear during a flu or cold, thus acquiring the name. Cold sores are caused by a virus, and can become bothersome, as they cause pain and have the tendency to reappear periodically.
Herpes Simplex Virus
The herpes simplex virus (HSV) type 1 infection causes cold sores. The herpes simplex virus (HSV) type 2 causes sores in the genital area, but either type of the virus can cause sores in the facial and genital area if exposed, according to the Mayo Clinic.
Primary Infection
According to the American Academy of Dermatology, two kinds of episodes can cause a cold sore outbreak--primary and recurrent. The first episode is the primary infection. This is the initial infection of the virus; it can be caused by contact with another person who has an active lesion. Individuals with the infection may experience pain and other symptoms, although some individuals may not exhibit any symptoms at all. However, even without symptoms, it's still possible to shed or pass the virus. The herpes simplex virus is contagious and can be passed by sharing eating utensils, razors and towels with someone who is infected. Kissing another person can also assist in the spreading and formation of cold sores. After the primary infection, cold sores may heal completely but the HSV will remain dormant in the body. The virus lies in the nerve cells in the skin and can become an active infection again.
Recurrent Infection
The second episode is referred to as a recurrent infection. A recurrent infection is the reactivation of the virus. This can occur in the same location as the previous infection or it can happen in a nearby site. The University of Maryland Medical Center reports that a recurrent infection is usually milder than a primary infection.
The American Academy of Dermatology reports that a variety of factors may contribute to a recurrent infection. Fever, sun exposure, menstruation, and trauma or surgery can cause cold sores to reappear. An infection can also occur without a known cause.
Other Causes
An immune system that's suppressed can cause a cold sore eruption. Emotional stress and wind have even triggered HSV, promoting an infection. Touching a cold sore, then touching an unaffected part of the body can spread the virus. Oral-genital contact can spread the virus as well. Dental work, such as a root canal or tooth extraction, can cause cold sores to emerge.
