Cold Sores

A cold sore (fever blister, oral herpes, herpes labialis) is a sore that appears most commonly around the mouth or on the lips.


Cold sores are caused by the Herpes Simplex Virus (HSV) and are transmitted by skin-to-skin contact with an infected person. HSV enters the body through small breaks in the skin, most commonly on or around the lips. Sometimes symptoms also appear on the chin, cheek, between the upper lip and the nose, or inside the mouth or nose.

Most people become infected with HSV for the first time during childhood, usually through kissing a family member. By adulthood, it often becomes a silent infection with no apparent symptoms.

There are two types of HSV. HSV‑1 most often causes cold sores, and HSV‑2 typically causes genital herpes. HSV‑1 can be easily spread from the mouth to the genitals through skin contact and/or oral sex, but HSV‑2 infection of the mouth, lips, or cheeks is rare.


When first infected with HSV the following stages of symptoms may occur:

  • The first symptoms (prodromal stage) usually include burning, tingling, or itching around the lips or nose starting 2 to 21 days after exposure.
  • Within 12 hours, small, red areas with fluid-filled blisters develop.
  • As blisters increase in size, they rupture and leak fluid. This stage is the most painful.
  • After blisters rupture, they form a hard crust and the sore heals, leaving a red, tender site.
  • Sometimes milder symptoms, such as chapped lips, a small crack or cut in the skin, a pimple, or a sore throat develop, especially with recurrences over time.


There is no cure for oral herpes. Treatment reduces the duration of the cold sore and can decrease the pain and other uncomfortable symptoms. Not all medications work for everyone. For a primary infection or for more treatment information, contact a clinician.

General treatment measures:

  • Ice: apply ice for five to ten minutes each hour during the tingle phase to numb the area and slow the development of the sore by decreasing the blood flow.
  • Astringent solution: apply a cold compress of an astringent solution, such as Domeboro solution 1:40 (available in pharmacies as a powder to dissolve in water), to help dry the sores, relieve pain, and reduce swelling.

Prescription medications:

  • Antiviral pills: prescribed for frequent or severe outbreaks. They are taken as soon as tingling or burning begins and may shorten the duration of the sore.
  • Antiviral cream: can be applied to the affected area as soon as pain or tingling begins, before the blister forms. It is used to aid the healing process and decrease viral activity.

Nonprescription medications:

  • Aspirin and acetaminophen: use according to directions for pain relief. If under the age of 19, aspirin is not recommended due to the risk of Reye’s syndrome.
  • Ibuprofen and naproxen: use according to directions to reduce swelling, redness, and pain.
  • Docosanol: works by stopping the virus from entering skin cells when it reactivates. It can be found in products such as Abreva.
  • Benzocaine, lidocaine, tetracaine, benzyl alcohol, camphor, and phenol: numbing agents used to relieve pain temporarily, not for healing.


The virus remains in the body but lies dormant in a bundle of nerves called the trigeminal ganglion and stops causing infection. The virus may become active again and cause recurrent cold sores. Cold sores typically recur three to four times a year, although some people may develop more than one cold sore per month. The frequency and severity of outbreaks generally decreases over time.

People often experience tingling, burning, or itching at the site prior to an outbreak. Outbreaks are often spontaneous, without a specific reason or cause, but some common triggers include:

  • overexposure to sunlight
  • stress
  • fatigue
  • illness
  • hormonal changes (premenstrual, pregnancy)
  • surgical procedures or trauma to the site.

To prevent recurrences, avoid trigger factors as much as possible:

  • Eat a balanced diet with at least five servings of fruits and vegetables daily to support a healthy immune system.
  • Get proper rest and exercise.
  • Manage or prevent stress.
  • Avoid trauma to the lips, such as chapped lips, or biting or peeling of lips.
  • Apply sunscreen to areas of the face or lips (using lip balm, SPF > 15) where cold sores appear.
  • Be careful shaving near sores. Shaving can spread the virus to other areas of the face.


The ability to infect others typically occurs when symptoms are present, including milder symptoms of tingling, burning, and itching. The virus can also reactivate without any symptoms, so a person can be contagious without having symptoms. Most of the time, the virus is inactive and cannot be transmitted.

HSV prefers warm, moist environments with soft tissue (mucous membrane) such as the mouth or genital area, but can also spread to tougher skin if a cut or break in the skin is present. Autoinoculation, which occurs by touching the site of the infection and then touching a cut or mucus membrane, is possible but unlikely after the first episode.

The following measures can reduce the likelihood of infecting others:

  • Wash hands thoroughly with soap and water after touching the sore. Do not touch the sore and then touch other parts of the body.
  • Do not share items that come in contact with the mouth of others such as lip balm, cups, straws, eating utensils, washcloths, razors, or cigarettes.
  • Do not put fingers in the mouth or bite fingernails.
  • Do not kiss people, especially children, if a sore is present.
  • Do not rub the eyes. Wash hands before applying makeup or putting in contact lenses. Never put contacts in the mouth. Although rare, herpes infections can be spread to the eye during the first outbreak and can cause sores on the cornea, which may result in cloudy vision, scarring, or blindness.
  • Avoid contact sports during an outbreak.
  • Do not engage in oral sex if an outbreak is present, including cold sores, genital sores, or feel an outbreak coming on, or if a partner is experiencing an outbreak. To further prevent transmission, use a barrier (condoms, sex dams, household plastic wrap) for oral sex.

When to contact a clinician

Any patient with HSV infection who develops eye symptoms should see a clinician immediately for an eye exam.