What are Cold Sores and Fever Blisters?

Cold sores are also known as fever blisters. These lesions are caused by the herpes simplex virus type 1 (HSV-1). It is very contagious and transmitted from one person to other by direct contact with infected skin or saliva. They appear as groups of painful, fluid-filled blisters. Cold sores occur mostly in the region of the lips, underneath the nose, or around the chin. Sometimes the HSV-1 infection can cause blisters inside the mouth on the gums and palate (roof of the mouth) as well that may become ulcers.

Initial infection with HSV causes fever, sore gums, sore throat and swollen or tender glands in the neck and it usually occurs in childhood.  The first infection appears like any other viral or bacterial throat infections, and is usually not diagnosed as an HSV-1 infection.

If you are once infected by herpes virus (HSV), it stays in the body forever. In some people the virus remains inactive and in others it can cause recurrent attacks of cold sores. About 20% of patients with HSV can have recurrent cold sores usually on the lip. These lesions are known as cold sores or fever blisters as cold or fever often reactivate the virus. The exact cause for reactivation is not yet known. Some other common trigger factors for cold sores are stress, dental treatment, illness, trauma to the lips, exposure to sunlight, menstruation, suppression of the immune system or allergies.

Besides causing cold sores around the region of the mouth HSV-1 can cause lesions in the eyes, the skin of the fingers, the genital area and elsewhere. Most of the infections in the genital region are caused by herpes simplex type 2 (HSV-2), but HSV-1 can cause genital infections at times. Severe infection due to HSV-1 can be caused in people--- with chronic health problems (such as malnutrition, cancer or suppression of the immune systems, including AIDS), on cancer chemotherapy, corticosteroids or immunosuppressive drugs.