What are cold sores?

Cold sores, sometimes referred to as oral herpes, are small blisters or lesions on the mouth, which are caused by the herpes simplex virus (HSV). The blisters can develop around the outside and inside the mouth.


Colds sores are caused by an infection with herpes simplex virus. There are two different forms of the virus that can cause cold sores, HSV1 and HSV2.

The viruses spread through contact with blisters or saliva from an infected person. Many people first become infected with herpes simplex virus during childhood. The virus lies dormant, and only sporadically becomes activated for short periods of time. There may be certain factors that trigger an outbreak of cold sores. They include:

  • Stress;
  • Exposure to sunlight;
  • Overexposure to wind;
  • Having a cold, the flu or another infection, and;
  • Menstruation.

Risk factors

You are more likely to get the infection that causes cold sores if you:

  • Come into direct contact with a cold sore;
  • Have contact with the saliva of a person with an active herpes simplex virus infection, or;
  • Have a weak immune system.

Signs and symptoms

Some people will experience a tingling, itching or burning feeling in the skin around the mouth before an outbreak of cold sores appears. Within a few days of forming, the blisters can burst and start to form a crust, which usually heals within 7-10 days.

When they first become infected with herpes simplex virus, some people may also experience:

  • Fever;
  • Muscle aches and pains;
  • Tiredness, and;
  • Tingling in the skin.

Once you contract the virus that causes cold sores, you have it for life. After the initial infection has cleared, the same virus can cause the symptoms to reappear periodically.

Cold sore on a lip.A cold sore typically forms a blister on the outside of the mouth. 

Methods for diagnosis

Doctors can usually identify cold sores from observation of the formed blister or lesion.

Types of treatment

There are treatments available that can help to relieve the symptoms of an outbreak and reduce the frequency of outbreaks.


Medicated antiviral creams, solutions or tablets, containing acyclovir, famciclovir or valacyclovir, may help to reduce the severity and duration of cold sores. Antiviral medications work best if they are started at the very first sign of a cold sore. They work by preventing the virus from replicating, which gives the immune system a better chance of bringing the infection under control.

If you experience outbreaks often, your doctor may prescribe an antiviral medication that can reduce the chance of developing symptoms.

Antiviral creams are used to reduce the severity and duration of a cold sore caused by herpes simplex virus. 

Self care

Using a cold compress, such as a wet face towel, on the affected area may help to relieve the itching and burning associated with a cold sore. Bathing the affected area with a salt bath may also provide some temporary relief from the itching and burning during the healing of the cold sore.

Potential complications

Cold sores can spread to areas of the body other than the mouth, including the eyes and genitals. Infection of the eyes can be very serious, as it can cause ulcers that may damage the cornea and eyesight. Infection near the genitals can lead to genital herpes.

Very rarely, the infection that causes cold sores can lead to meningitis. This occurs when the thin layers of membrane surrounding the brain and spinal cord become inflamed.


An open sore in the skin or mucous membranes such as those of the stomach lining, intestine or mouth.


Having cold sores is not usually very serious. They generally improve on their own without leaving any lasting damage to the skin.


There are several things you can do to reduce the chance of contracting the herpes simplex virus that causes cold sores. They include:

  • Avoid kissing someone with a cold sore;
  • Avoid oral sex if your partner has genital herpes; and;
  • Avoid sharing food, cutlery and other personal items of people with cold sores.

If you have the herpes simplex virus, then avoiding the factors that can trigger an outbreak, such as stress and exposure to sunlight, may reduce the chance of developing cold sore symptoms.


  1. Cold sores. Better Health Channel. Accessed 22 July 2014 from link here
  2. Murtagh J. MD. (2011). John Murtaghs General Practice (5th Revised edition edition.). North Ryde N.S.W.: McGraw-Hill Medical Publishing.
  3. The Cochrane Collaboration (ed.). (1996). Cochrane Database of Systematic Reviews: Protocols. Chichester UK: John Wiley & Sons Ltd. Accessed from link here

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