Cold sore

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 25, 2016
StartDiseasesCold sore

Cold sores, sometimes known as fever blisters or oral herpes are a common viral infection caused by a contagious virus called herpes simplex type 1 (HSV-1). Cold sores usually contain fluid and appear in clusters or patches on or around the lips. They are not to be mistaken for canker sores, which are sores involving the mucous membrane not caused by a strain of the herpes virus.


Definition & Facts

Resulting from exposure to the herpes simplex virus, these small and sometimes painful blisters are fluid-filled and most commonly form in clusters and groups outside of the mouth, on or around the lips, chin, cheeks, and in some cases, inside the nostrils of the nose. In rare cases they can also occur inside of the mouth, usually affecting the roof of the mouth or the gums. Once they burst and their fluid oozes out, the subsequent sores are covered by a quick-forming crust while they heal over an average of 2 to 4 weeks. Most cold sores will heal in a month or less without leaving a visible scar.

Symptoms & Complaints

Some people do not experience any symptoms from the infection that causes cold sores, and therefore are unaware that they are in fact infected. Others experience painful cold sores that heal over the course of three stages and are usually accompanied by the following symptoms:

  • Tingling and itching. During this phase, many individuals report having intense feelings of itchiness, burning, or tingling around their lips in the day or 2 prior to the appearance of a small, hard, and painful spot that eventually becomes a blister(s).
  • Blisters. This phase is marked by the visible appearance of blisters that typically form along the edges of the mouth and lips. This location where the skin of the face touches the lips is the preferred breeding grounds for cold sores, though they have been known to appear in the nostrils and across the cheeks.
  • Oozing and crusting. During this third phase, the blisters could possibly merge (though this does not happen in all cases) and erupt and fluid emerges from the vulnerable open sores. Finally, a crust forms over the sore.

As with most infections and conditions, the symptoms can be different for each person, depending on whether this is the individual's first outbreak or a recurring event. It is quite common for the first outbreak to be the most severe, even though recurrences typically appear in the same area each time. These initial symptoms can include:


Certain strains of the herpes simplex virus (HSV) are known to cause cold sores. Type 1 (HSV-1) is typically to blame for oral herpes, or cold sores, on the mouth and lips, while herpes simplex type 2 (HSV-2) typically causes herpes outbreaks on the genitals. However, both strains of HSV can be responsible for cold sores of the genitals and facial area.

A large majority of the people who become infected with the virus that causes cold sores will never develop any signs or symptoms, even though up to half of the U.S. population will be infected by the herpes virus by the time they reach their mid-20's.

The most contagious time for anyone suffering with cold sores is during the oozing phase, when it is extremely easy to infect another person. Technically, however, caution should always be used since cold sores can be spread even when blisters are not present.

There are several common methods of transferring the HSV-1 virus, including:

  • Sharing utensils
  • Sharing razors and/or bath towels
  • Kissing

Additionally, oral sex can transfer HSV-1 to the genitals and HSV-2 to the lips. Once an individual experiences an episode or series of symptoms related to a herpes infection, the virus will continue to lie dormant within the person's skin nerve cells and show up at a later time as a cold sore in the same spot as the first outbreak or possibly in a new area. These recurring bouts of cold sores can be triggered by certain factors including:

Diagnosis & Tests

Most cold sores heal on their own and do not require treatment by a physician. When medical care is sought, most doctors can diagnose cold sores just through visible observation. To confirm the diagnosis, he or she may collect a sample from one of the blisters to send to the laboratory.

While the pain and discomfort associated with cold sores is usually pretty mild and manageable, it may be necessary to see a doctor if:

  • Immune system has been weakened
  • Cold sores do not heal or seem to improve within 2 weeks
  • Symptoms are more severe than expected
  • Cold sores recur in frequent intervals
  • Unusual irritation occurs in the eyes

Treatment & Therapy

There is no cure for the herpes virus, so once a person experiences a cold sore outbreak for the first time, it is possible that the blisters will return. Despite there being no permanent solution or cure for the virus and its many symptoms, certain antiviral drugs have been proven to promote faster healing and the frequency in which they recur.

Prescription anti-viral medications (some of which are in pill form, others are creams and ointments) such as acyclovir, valacyclovir, famciclovir, and penciclovir are sometimes used to promote faster healing. The pills are generally considered more effective, though the ointments are effective at numbing the blisters, and the ointments are generally an effective solution for softening the crust that forms around the open sores after they've burst.

Home remedies also exist such as:

  • Over-the-counter ointment such as docosanol to reduce the length of an outbreak. This ointment should be applied frequently.
  • Lip balms and creams to protect lips from sunlight and wind exposure.
  • Application of a cold compress to reduce redness and soften the crust covering the sores.
  • Over-the-counter creams with lidocaine or benzocaine to provide temporary pain relief.

Some people even try oral supplements and creams containing lysine, synthetic beeswax, and rhubarb and sage as alternative methods for relieving their discomfort. Some believe stress reduction also goes a long way in helping these blisters to heal more quickly.

Prevention & Prophylaxis

Some doctors will prescribe an anti-viral medication that should be used on a regular basis to prevent secondary bacterial infections. Other preventative methods include:

  • Avoiding close physical contact with anyone who has already been diagnosed with the herpes virus, specifically while blisters are present.
  • Regular hand washing
  • Avoid sharing drinks, utensils, towels, and more