Cold sores (also called herpes labialis) are small blisters that usually form on the lips or skin around the mouth, nose and on the chin. They are caused by infection with the herpes simplex virus (HSV). People are usually infected in childhood or young adulthood, and the infection persists for life.

Between 70 and 90% of adults have herpes simplex antibodies in their bloodstream, which means that they have been infected with the virus at some time.

However, the first (or primary) infection does not usually cause any symptoms

Around one-third of infected people experience cold sores, which are a recurrence of the earlier infection and do not indicate recent infection.

Most of these people would not have experienced symptoms from the first infection. For some people (mainly children) infected with HSV, the first (primary) infection can cause symptoms. These can include: swollen lymph nodes near the infection.

The symptoms can last up to 14 days and may cause dehydration, especially in young children, because it is painful to swallow. Primary infections are more likely to be severe in newborn babies, people with and in people with a weakened immune system. This explains the term ‘cold sore’.

Other triggers that may cause an attack of cold sores include: emotional or physical stress. It is important to remember that cold sores are a symptom of ongoing infection rather than a new infection.

The sores usually recur in the same place

Cold sores usually develop as follows: Most people experience localised itching and tingling a day or 2 before the cold sore appears.

A collection of small blisters forms

These blisters can be accompanied by pain, tenderness and a sensation of heat and burning.

The blisters burst after a few days

The site develops a crust

The crust dries up and eventually falls off after about 10 days. Cold sores are an annoying problem for most people who get them, but they get better without any specific treatment. or taking very high doses of corticosteroids such as prednisolone), the cold sores can spread more widely and the symptoms can be more severe.

Antiviral medication may be required in these cases

Uncommon complications that require medical attention include:

  • cold sores that spread to the eyes
  • fingers or other parts of the body – a cold sore in the eye causes a painful red eye. Immediate medical attention should be sought
  • as the herpes virus causes an ulcer on the cornea that can damage sight

However, permanent damage can usually be prevented by early treatment, including medication to suppress the virus.

There are other more common causes of a painful red eye, which also require medical review. There are 2 types of herpes simplex infection: herpes simplex virus type 2 (HSV-2). Cold sores around the mouth (often called ‘oral herpes’) are generally caused by HSV-1.

Most cases of are caused by HSV-2

For people who do not already carry the cold sore virus (HSV-1). There are many other viruses that are also in the herpes virus family, however the infection and symptoms are different. One example is varicella zoster virus (VZV) which causes HSV spreads between people, usually through contact with saliva or direct contact with a blister.

The most infectious time is in the first few days when the blister is forming.

Sometimes, people can pass the virus to others when they have no symptoms

This is because the virus may be lying dormant in the skin cells of the lips.

If you have a cold sore, be sure to wash your hands after touching it and be especially careful to avoid touching your own eyes after touching your cold sore. It is the fluid contained in the blisters that is considered to be the most infectious. While you have a cold sore it is also important to avoid: close contact with people with weakened immune systems.

If young children with a cold sore are unable to follow good hygiene practices, they should be excluded from childcare or school until the blister stops weeping. Blisters should be covered by a dressing, where possible. Cold sores are generally not dangerous and do not cause any permanent damage to the skin.

Treatment does not cure the infection and is not necessary for most cases. Avoid picking the scab or breaking blisters as this can cause secondary infection with bacteria, or scarring.

Creams to treat the symptoms can be soothing, as can ice on the blisters

Simple painkillers may occasionally be required

Povidone-iodine ointments (commonly known as Betadine) can be dabbed onto the cold sores and may reduce symptoms in some people.

Antiviral medications come in many forms, including creams and tablets

Medications such as aciclovir and famciclovir shorten the duration of the cold sore by reducing the ability of the virus to reproduce.

Aciclovir cream works best when applied to the blister at the earliest stages of cold sore development, when the area is tingling.

However, not everyone experiences warning signs of an impending cold sore.

There is no cure for cold sores

Suggestions to reduce the number of outbreaks include:

  • Avoid known triggers
  • if possible. Wear sunblock on your face
  • lips when outdoors. Pay attention to your general health
  • stress levels

Avoid getting ill or run down

About cold sores Herpes simplex virus (HSV) infection is very common Symptoms of a primary herpes simplex virus (HSV) infection fever headache malaise muscle aches blisters (lesions)

  • and ulcers in around the mouth pain swelling inside the mouth
  • on the gums a sore throat atopic dermatitis (often called eczema) Triggers for cold sores In some people the HSV infection causes cold sores
  • which erupt following a trigger event such as a cold feverish illnesses
  • like influenza (flu)
  • or chest infections exposure to sunlight exposure to windy conditions hormonal changes
  • such as the menstrual period Cold sore symptoms Cold sore complications However
  • in people with some types of immunosuppression (such as people undergoing chemotherapy bacterial infections – possible symptoms include redness around the blisters
  • pus in the blisters
  • fever Types of herpes infection herpes simplex virus type 1 (HSV-1) genital herpes Cold sores on the mouth can cause genital infection during oral sex chickenpox
  • hugging) with newborn
  • advice (24 hours
  • days) Your local pharmacist

Key Points

  • They are caused by infection with the herpes simplex virus (HSV)
  • However, the first (or primary) infection does not usually cause any symptoms
  • Most of these people would not have experienced symptoms from the first infection
  • For some people (mainly children) infected with HSV, the first (primary) infection can cause symptoms
  • Other triggers that may cause an attack of cold sores include: emotional or physical stress