Cold sores, also called fever blisters, are clusters of small blisters on the lip and outer edge of the mouth caused by herpes simplex virus-1 (HSV-1.) Herpes simplex virus-1 is different than herpes simplex virus-2. Herpes simplex virus-2 is the virus that most often leads to genital herpes. This article only covers HSV-1, the herpes virus that leads to mouth and lip sores.

HSV-1 can enter the body through a break in the skin around or inside the mouth. It is spread through coughing, sneezing, direct contact with a cold sore, or by sharing things that a person who has a cold sore has used. It is common for a parent to unknowingly spread the virus to his/her child. Once infected, HSV-1 cannot be cured and remains in the body causing cold sores to return throughout life.

Most people experience three to four outbreaks per year. Outbreaks are triggered by infections, fever, stress, trauma, hormonal changes, exposure to sunlight, or food allergies. Cold sores will usually break open, crust over, and disappear after several days.

Treatment options can reduce the duration, number, and severity of outbreaks and may include lifestyle recommendations, over-the-counter medications, and alternative treatments. Some lifestyle recommendations may include avoiding triggers such as spicy foods, stress, overexposure to the sun, and addressing hormonal changes with your physician. Over-the-counter medicines include ointments or topical creams that may help soothe painful blisters. Anti-viral medicines may also be recommended to lessen the duration of cold sores. Alternative treatments that may provide some relief include vitamin C, L-lysine, and lemon balm.

Vitamin C may be ingested, applied directly on the cold sore, or both to help lessen the duration of cold sores. Some experts recommend a combination of a liquid vitamin C soaked cotton pad applied to the cold sores several times a day along with an oral dose of vitamin C, 500 to 600 milligrams (mg)/day. Small studies support the use of both oral and topical vitamin C for lessening the duration of cold sores.

Lemon balm cream has been shown to help reduce the number and duration of outbreaks and is most effective when the cream is applied to cold sores 2 to 4 times daily.

L-lysine may be helpful in inhibiting HSV-1 outbreaks, and also lessening the duration and severity of them. One study found that those taking 1000 mg of L-lysine 3 times daily (3000 mg daily) for 6 months had fewer outbreaks, less severe symptoms, and reduced healing times. Another study using 1,248 mg of L-lysine daily found a reduction in the number of outbreaks, but did not see a reduction in the duration of the outbreaks.

Dose recommendations vary from 500 to 3000 mg L-lysine daily for HSV-1. Some doctors suggest 1000 to 3000 mg of L-lysine daily during the early symptoms and outbreak phase; and 500 to 1000 mg of L-lysine daily to inhibit recurrences of outbreaks. If taking lysine, limit intake of arginine-containing foods as arginine may decrease lysine absorption. Foods rich in arginine include chocolate, peanuts, almonds, seeds, cereal grains, gelatin, and raisins.