After this first infection, the virus remains dormant (inactive) in the nerves of the face. In some people, the virus becomes active again from time to time. When this happens, cold sores appear.
HSV-1 can get active again because of a cold or fever.
Stress also can lead to a cold sore outbreak. This includes mental and emotional stress, as well as dental treatment, illness, trauma to the lips or sun exposure. HSV-1 also can infect the eyes, the skin of the fingers and the genitals. Most genital herpes infections are caused by herpes simplex type 2 (HSV-2), however.
HSV-1 can cause serious illness in people who have other health problems. The virus also can cause serious illness in people whose immune systems are weakened by either illness or medicines they are taking.
Cold sores appear when HSV-1 is reactivated later in life. They may occur after a period of illness or stress, poor nutrition or sunlight exposure. Sometimes there's no known reason. Dental procedures that stretch the lip may occasionally trigger the virus.
The border of the lip is the most common place that these sores appear. They may occasionally occur inside the mouth, too. This is more likely in people who have weakened immune systems or other medical problems.
The first sign of a cold sore is a tingling, burning or itching. This is followed by swelling and redness. Within 24 to 48 hours, one or more tiny blisters ("fever blisters") appear. These blisters pop and form painful sores ("cold sores"). The sores eventually are covered by crusts, which look like scabs. The crusts are shed and form again while the sore heals.
There is evidence that using sunscreen on your lips will prevent cold sores caused by sun exposure. Antiviral medicines may prevent cold sores from forming. In certain situations, your dentist or physician may prescribe these medicines. If you expect to encounter a known trigger, a medicine taken in advance can decrease the chance of a cold sore.
These drugs also can stop cold sores from popping up in the first place. Some people take them when they know they will be under stress.
Keep the area clean and apply lip balm. Try not to touch the area. Avoid kissing anyone while you have blisters and sores.
Centers for Disease Control and Prevention (CDC)
Division of Oral Health
4770 Buford Highway, NE
MS F-10
Atlanta, GA 30341
Phone: (770) 488-6054
Toll-Free: (888) 232-3228
Fax: (888) 232-3299
E-Mail: oralhealth@cdc.gov
www.cdc.gov/OralHealth