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Cold sores (oral herpes)

Cold sores are small, fluid-filled blisters that develop around the lips or inside the mouth. Cold sores are caused by herpes simplex virus (HSV). HSV infection is passed on through skin-to-skin contact such as kissing.

About cold sores

There are two types of HSV, HSV-1 and HSV-2. Cold sores are mainly caused by HSV-1. HSV-2 can also infect the mouth, although it mainly causes genital herpes.

About eight in 10 people have HSV-1 antibodies – meaning they have the virus. From the first time you get HSV (primary infection), the virus stays in your body for the rest of your life.

Symptoms of cold sores

The primary infection with HSV can develop in different ways. It may cause mild symptoms or no symptoms at all. Children under five are most likely to be ill from a primary infection. Your child may have:

  • a high temperature and a headache
  • swollen and painful gums (gingivitis)
  • blisters inside the mouth (stomatitis).

Blisters will usually appear one to three weeks after getting the virus and last for 10 to 14 days.

As a primary infection in adults, HSV may cause a glandular fever type illness (sore throat and swollen tonsils with fever and headache).

After the primary infection, with or without symptoms, the virus lies dormant in your body but can reactivate and cause blisters on the lips (cold sores).

Recurrent outbreaks usually start with a tingling sensation, redness and swelling around the lip. This is followed by small, fluid-filled blisters, which break open and develop a yellow crust (scab). The scab usually falls off around seven days later.

Recurrent outbreaks usually occur in or around the same place each time. It's possible to have two to three outbreaks a year.

Complications of cold sores

The sores can become infected with bacteria and cause impetigo.

Cold sores can spread to other areas of skin such as the fingers, eyes or genitals. If the virus spreads to the eyes, it can damage vision. If it spreads to the genitals, it can cause genital herpes.

The virus can spread into broken skin (for example, eczema or dermatitis) and cause a serious skin infection.

If you have symptoms of either primary or recurrent HSV infection and you have a weakened immune system (for example, if you have HIV/AIDS or are taking medicines that suppress your immune system), you should visit your GP. There is a risk the virus may cause serious illness.

Although rare in Australia, there is a risk that you can pass HSV infection to your baby in pregnancy, during the birth or immediately after birth. This is known as neonatal herpes and can cause your baby to be seriously ill. This is more of an issue if you have genital herpes. But if you have any symptoms of a primary HSV infection or cold sores for the first time when you are pregnant, particularly in the later stages of pregnancy, you should see your GP or obstetrician for advice.

Causes of cold sores

Cold sores are usually caused by HSV-1 and the infection is passed through skin-to-skin contact such as kissing someone who has the virus or by sharing objects which have been in contact with the virus, such as a razor or a lipstick.

There are several factors that can trigger an episode of cold sores, including:

  • emotional stress
  • tiredness/feeling run down
  • menstruation
  • strong sunlight on the lips
  • an injury to the mouth or a dental procedure
  • fever.

For many people, however, the trigger is unknown.

Diagnosis of cold sores

Usually, your GP will be able to recognise cold sores (or oral herpes infection) from looking inside and around your mouth. Your doctor may take a swab from the blister and send it to a laboratory to confirm that you have the herpes virus.

Treatment of cold sores

There is no treatment that can get rid of the herpes virus from your body. Once you are infected, it will remain in your body, even if you never get any symptoms.

Cold sores usually clear up within a week or so. There are steps that you can take to help relieve any pain or discomfort from cold sores and prevent them spreading.

  • Take a non-prescription painkiller, such as paracetamol or ibuprofen, to ease any pain or discomfort.
  • Non-prescription anti-viral cold sore creams can help the cold sore clear up more quickly, particularly if applied when you first notice symptoms, such as a tingling sensation around your lips. Don't share cold sore creams with anyone else.
  • Non-prescription moisturising creams and liquids can ease irritation once the cold sore has developed.
  • Occasionally, if the infection is particularly severe or frequent, your GP may prescribe anti-viral tablets.
  • Try not to touch the sores and if you do, wash your hands to prevent spreading the infection.
  • Don't kiss or have oral sex until you (or your partner's) cold sores have completely healed.
  • Don't share any objects that may have been in contact with the virus such as a lipstick or lip-gloss, razor, face towel or cutlery.
  • Wash your hands thoroughly before putting in your contact lenses. This is to prevent HSV infection spreading to your eyes.

Always read the consumer medicine information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.

Treatment for blistering of the mouth and gums

If you or your child has severe blistering of the mouth and gums, the following steps may help ease any pain or discomfort.

  • Take a non-prescription painkiller, such as paracetamol or ibuprofen, to ease any pain or discomfort. Children can take liquid painkillers. Always read the consumer medicine information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.
  • Drink enough fluids to stop dehydration; this is particularly important in young children.
  • Eat cool, soft foods and don't eat foods which are salty, acidic or spicy.
  • Use a lip barrier cream (such as Vaseline) to stop your lips sticking together.
  • Visit your GP. They may prescribe a cream to help relieve pain and may also give you a mouthwash to help maintain good oral hygiene if brushing your teeth is painful.

Prevention of cold sores

There are ways that you can lower your risk of getting or passing on cold sores and preventing recurrent episodes.

  • Use sun block or a lip balm with an appropriate sun protection factor (SPF 15 or higher) on your lips to stop overexposure to sunlight.
  • Don't kiss someone who has a cold sore.
  • Don't have oral sex if you or your partner has a cold sore or has genital herpes.
  • Don't share any creams, medicines, make-up or any object, which may have come into contact with an infected area.
  • Have good hand hygiene to stop spreading infection to other areas of your body.

Stress and feeling run down can trigger recurrent episodes of cold sores. Taking measures to prevent feeling stressed or run down can also help reduce your risk of having an outbreak.

Further information

Australian Herpes Management Forum


Australian Herpes Management Forum (AHMF). Guidelines for clinicians managing oral herpes. [online] Sydney, NSW: AHMF. [Last updated 2009, accessed 7 Jul 2011] Available from:

Better Health Channel. Cold Sores. [online] Melbourne, VIC: State Government of Victoria. c1999-2010 [Last reviewed Jul 2010, accessed 7 Jul 2011] Available from:

Clinical Knowledge Summaries. Herpes simplex – oral. [online] London: National Institutes for Health and Clinical Excellence. 2007 [last updated Apr 2009, accessed 7 Jul 2011] Available from:

Hollier LM Wendel GD. Third trimester antiviral prophylaxis for preventing maternal genital herpes simplex virus (HSV) recurrences and neonatal infection. Cochrane Database of Systematic Reviews, 2008, Issue 1. Art. No.: CD004946. DOI:10.1002/14651858.

CD004946.pub2 [online] Available from:

MyDr. Cold sores overview. [online] St Leonards, NSW: UBM Medica Australia. 2000 [Last reviewed Aug 2007, accessed 7 Jul 2011] Available from:

MyDr. Cold sore infections. [online] St Leonards, NSW: UBM Medica Australia. 2001 [Last reviewed Jul 2010, accessed 7 Jul 2011] Available from:

Pharmacy Self Care. Cold sores (herpes simplex). Deakin, ACT: Pharmaceutical Society of Australia. 2011.

Sheary B Dayan L. Herpes simplex virus serology in an asymptomatic patient.Australian Family Physician. 2005; 34(12): 1043–1046.


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