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Cold sores

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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.

Causes

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:

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:

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.

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.

Medication

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.

Prognosis

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

Prevention

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

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.

References

  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

8 Most frequently asked questions (FAQs)

What is a cold sore?
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).
Are cold sores contagious?
The herpes simplex virus that causes cold sores is contagious. The viruses spread through contact with blisters or saliva from an infected person.
What causes a cold sore?
Cold sores are caused by an infection with a virus called the herpes simplex virus (HSV). There are two different forms of the virus that can cause cold sores, HSV1 and HSV2.
How are cold sores treated?
Medicated antiviral creams, solutions or tablets, containing acyclovir, famciclovir or valacyclovir, may help to reduce the severity and duration of cold sores. 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.
What can trigger a cold sore?
An outbreak of cold sores can be caused by stress, sunlight or wind exposure, having a cold, the flu or another infection, and menstruation.
How can I prevent getting cold sores?
To prevent contracting the herpes simplex virus that causes cold sores: 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.
Can cold sores cause genital herpes?
Yes, cold sores around the mouth can sometimes spread to the genitals during oral sex, resulting in genital herpes.
Can I get cold sores from kissing someone with a cold sore?
Yes, you can catch cold sores from kissing someone who has them. The virus that causes cold sores can be passed on through direct contact with the cold sores, or through contact with the saliva of an infected person, which can occur during kissing.

Related topics

Chickenpox

Chickenpox is a common, contagious childhood illness, caused by the varicella virus. It causes a distinctive, itchy rash, and normally resolves on its own. A vaccine is available that can help reduce your chance of getting the condition.

Contact dermatitis

Contact dermatitis is inflammation of the skin caused by direct contact with an irritant or something that induces an allergic reaction. It commonly presents as a red, itchy skin rash usually on the hands or face. Avoiding the cause once identified can prevent it happening it the future.

Genital herpes

Genital herpes is a common sexually-transmitted infection that is caused by a virus. Some people with the condition will not experience any symptoms, while others will develop small blisters or ulcers on or around their genitals. Following some advice can help reduce symptoms and help prevent spreading the virus.

Hypoparathyroidism

Hypoparathyroidism occurs when the parathyroid glands are underactive and don’t produce enough parathyroid hormone (PTH). In turn, this underproduction of PTH causes low levels of calcium to be absorbed into the blood from the bones and food.

About this article

Title: Cold sores

Author: Dr Joanne Van der Velden PhD, BSc (Hons)

First Published: 22 Sep 2014

Last reviewed: 17 Jan 2022

Category: Information on Cold sores

Average rating: 4.9 out of 5 (2682 votes)

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