Cold Sores

What are Cold Sores?

Cold SoreCold sores are caused by a virus called Herpes Simplex (HSV-1). They are also known as “Fever Sores”, “Oral Herpes” or “Herpes Labialis”. The virus is spread from person to person by saliva (either directly, or by drinking from the same glass or cup) or through skin contact. Cold sores usually appear as clusters of tiny blisters on the lip. Most people are first infected with HSV-1 before the age of 10!. They are extremely common and it is reckoned that about 4 out of 5 Irish people have been exposed to the virus.

After being infected for the first time, the virus remains inactive in the nerves of the face. For some, the virus becomes active again every once in a while. When this happens, cold sores appear.

What triggers Cold Sores?

Cold sores usually appear when HSV-1 is reactivated, later in life. They may occur after a period of illness or stress, poor nutrition or sunlight exposure; feeling under the weather (e.g. the common cold) can also activate the virus. Sometimes however, there is no actual reason. Dental procedures that stretch the lip can occasionally trigger the virus.

The virus can actually cause serious illness in people who have other health problems or have weakened immune systems.

Signs & Symptoms

The first time someone is exposed to the virus, symptoms usually present about a week afterwards; people may experience fever, headache, nausea and vomiting. The mouth can often be sore to open and can be painfully swollen. Some people also complain of having a sore throat.

The border of the lip is the most common place that these sores appear. They may occasionally occur inside the mouth, too. This is more likely in people who have weakened immune systems or other medical problems.

The first sign of a cold sore is a tingling, burning or itching. This is followed by swelling and redness. Within 24 to 48 hours, one or more tiny blisters (“fever blisters”) appear. These blisters pop and form painful sores (“cold sores”). The sores eventually are covered by crusts, which look like scabs. The crusts are shed and form again while the sore heals.

How long will they last?

When you are first infected with HSV-1, symptoms can last for 1-2 weeks. Cold sores usually crust within 4 days and heal completely within about 7 to 10 days.

Can I prevent them from occurring in the first place?

To help to prevent a first herpes infection in children, the best thing to do is to not let them be kissed (!!) by anyone who has cold sores or signs of a first herpes infection!

HSV-1 is very common. Most children will be infected by the time they become adults. Several different vaccines are being developed against HSV (types 1 and 2), but these appear to protect only people who have never been infected.

There is evidence that using sunscreen on your lips will help prevent cold sores caused by sun exposure. Antiviral medications may prevent cold sores from forming. In certain situations, your dentist or GP may prescribe these medications. If you expect to encounter a known trigger, medicine taken in advance can decrease the chance of a cold sore.


Cold Sore Treatment with ZoviraxAs we mentioned above, some medications can help cold sores heal faster and will also relieve pain and discomfort. Commonly prescribed medicines in Ireland would include acyclovir (‘Zovirax’) and famciclovir (‘Famvir’). Its important to note that these medications won’t actually get rid of the virus. You should take them each time you can feel a cold sore coming on. Once you have blisters on your lip, the medicines won’t actually help much. Some people instinctively will take them when they know they will be under stress.

Keep the area clean and apply lip balm. Try not to touch the area. Avoid kissing anyone while you have blisters and sores!

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