Cold sores are a common viral infection, often appearing as small blisters on or around the lips. They are primarily caused by the herpes simplex virus type 1 (HSV-1), though herpes simplex virus type 2 (HSV-2) can also be responsible. This virus is widespread, with over 65 percent of individuals under the age of 50 globally having HSV-1. In the United States, between 50 and 80 percent of adults carry the oral herpes virus.
How Cold Sores Spread
Cold sores are highly contagious, particularly during an active outbreak when blisters are present and fluid-filled. The primary method of transmission is direct skin-to-skin contact, such as kissing. The virus can also spread through sharing personal items that have come into contact with the sore or saliva, including eating utensils, drinking cups, lip balm, razors, or towels.
While the risk is highest during a visible outbreak, the virus can still be transmitted even when no sore is apparent, a process known as viral shedding. Cold sores are considered contagious from the moment an individual first feels a tingling sensation, which often precedes the appearance of a sore, until the sore has completely healed and the scab has fallen off. This contagious period can last approximately two weeks.
What Happens If You Contract the Virus
Upon initial exposure to HSV-1, a person may or may not develop symptoms. If symptoms occur, this is known as a primary outbreak, which can be more severe than subsequent episodes. Common symptoms of a primary outbreak include the development of fluid-filled blisters around the mouth, along with pain or tingling at the site. Some individuals may also experience flu-like symptoms such as fever, a sore throat, swollen lymph nodes, body aches, and fatigue.
Once contracted, HSV-1 remains in the body indefinitely, establishing a dormant state within the nerve cells. The virus can reactivate periodically, leading to recurrent cold sore outbreaks. Various triggers can cause the dormant virus to become active, including physical or emotional stress, other illnesses or fevers, intense sun exposure, hormonal changes like menstruation, or trauma to the mouth area. Recurrent outbreaks typically present as localized blisters and are less severe and shorter in duration.
Preventing Transmission
To prevent the transmission of cold sores, especially during an active outbreak, individuals should avoid close physical contact, such as kissing. Also refrain from sharing personal items that come into contact with the mouth, including eating utensils, drinking glasses, lip balms, or toothbrushes. Practicing good hand hygiene is important; hands should be washed thoroughly with soap and water after touching a cold sore.
Avoid touching the cold sore and then other body parts, particularly the eyes or genitals. Individuals with cold sores should also exercise extra caution around vulnerable populations, such as newborn babies and those with weakened immune systems, as HSV-1 can cause severe complications in these groups. Minimizing known triggers can also help reduce the frequency of outbreaks.
Managing a Cold Sore Outbreak
When a cold sore outbreak occurs, several approaches can help manage symptoms and accelerate healing. Over-the-counter (OTC) topical creams can help shorten the duration and severity of the outbreak if applied at the first sign of symptoms, such as tingling. Other OTC products with numbing agents can provide temporary pain relief.
Prescription antiviral medications, available as oral tablets or topical creams, are effective in treating cold sores. Common examples include acyclovir, valacyclovir, and famciclovir. These medications work best when initiated early in the outbreak, ideally within 24 to 48 hours of the first symptoms, to significantly reduce healing time. Avoid picking or squeezing the cold sore, as this can lead to secondary bacterial infections or further spread the virus. Keeping the area clean with gentle washing supports healing.