A cold sore (fever blister, oral herpes, herpes labialis) is a sore that appears most commonly around the mouth or on the lips.
While there is no cure for oral herpes, treatment can reduce the duration of the cold sore and can decrease the pain and other uncomfortable symptoms. Not all medications work for everyone.
When to contact a clinician
Any patient with HSV infection who develops sores near the eye, red eye, or eye pain, should see a clinician immediately for an eye exam, or if you have a fever or concerns for other severe symptoms.
Causes & Symptoms
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.
There are two types of HSV. HSV-1 most often causes cold sores of the mouth and lips, and HSV-2 typically causes genital herpes. However, HSV-1 can be spread to the genitals through oral sex, and rarely HSV-2 can cause sores on the mouth and lips.
- Burning, tingling, or itching around the lips or nose starting two 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.
General treatment measures
- Ice: apply ice for five to 10 minutes each hour during the tingle phase to numb the area and slow the development of the sore by decreasing the blood flow.
- 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.
- Antiviral pills are prescribed for frequent or severe outbreaks. Take as soon as tingling or burning begins and they 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. Creams are generally not as effective as pills.
- Aspirin and acetaminophen can be used according to directions for pain relief. Aspirin is not recommended for students under the age of 19 due to the risk of Reye’s syndrome.
- Ibuprofen and naproxen can be used according to directions to reduce swelling, redness, and pain.
- Docosanol (brand name Abreva) is a cream that can help cold sores heal. It works by stopping viral entry and replication in the skin cells. It is applied 5 times daily starting at the first sign of a cold sore, and used until it heals, up to 10 days.
- Benzocaine, lidocaine, tetracaine, benzyl alcohol, camphor, and phenol are numbing agents used to relieve pain temporarily, not for healing.
Recurrence & Prevention
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
- Hormonal changes (premenstrual, pregnancy)
- Surgical procedures or trauma to the site
To prevent recurrences, avoid trigger factors as much as possible, and:
- 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 body parts.
- Do not share items that come in contact with the mouth of others such as lip balm, cups, straws, eating utensils, washcloths, razors, vape pens, or cigarettes.
- Do not put fingers in the mouth or bite fingernails.
- Do not kiss people, especially children, when 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. Using a barrier for oral sex (condoms, sex dams, household plastic wrap) may decrease the chance of transmission