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Cold Sore

Herpes labialis (Latin name)

By Bjarne Lühr Hansen PhD, MD and Philipp Skafte-Holm MD, Mentor Institute

Cold sore is a contagious illness caused by a viral inflammation (Herpes simplex). The illness appears as stinging blisters and painful wounds in the mouth and on the lips. The illness has a tendency to return again and again – often simultaneous with a severe common cold. Call the doctor immediately, if the cold sores spread to the nose or the eyes.

Cold sore is a contagious illness caused by a viral inflammation (Herpes simplex). Often, the illness starts with redness and an unpleasant prickly sensation in the skin where the blisters appear later. After a few days, small blisters filled with fluid develop which quickly bursts and become sores. The sores are covered by a crust that typically falls off after 8 to 10 days. The blisters and the sores are placed on the lips and inside the mouth.

The worst part about cold sores is that they have a tendency to return again and again. When you have had your first outbreak of cold sores, there is always a risk that they might return. Typically, they return in connection with a common cold (hence the name cold sores) or another infection. Also sunlight can make the sores return. One in every 5 people has repeated outbreaks of cold sores throughout their lives.

All children can become infected with the illness but most children have their first outbreak of cold sores, when they are 3 to 5 years old. It is expected that 80% of all adults have had cold sores, at some point in their life.

With the smallest children (1 to 3 years), the illness appears as an inflammation of the oral cavity. Inside the mouth, on the inside of the cheeks and gums, the mucous membrane appears red and covered with blisters. It is common that the child, at the same time, has a light fever.

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Most children are infected from a healthy carrier which means that the person has the virus but no cold sores or blisters. Therefore, it is difficult to avoid spreading of the illness. When the child has an outbreak, it infects by direct touch with fluid from the blisters. The child is contagious until a crust covers all the sores.

Day care:
A child with a cold sore can attend day care and school. Cleanliness and washing of hands can reduce the risk of spreading the illness.


There is medication that can shorten the duration of the illness but it cannot kill the virus. If it is a few blisters or sores, they are treated with a crème. The treatment should begin as soon as possible – preferably, already when the prickly and stinging sensation begins. In the case of larger outbreaks or frequent outbreaks, treatment with tablets is an option. For the smaller children with an inflammation of the oral cavity the medication exists as lemonade (mixture).

Children with an inflammation of the oral cavity usually do not want to eat or drink because it hurts in the mouth. In those cases, it can be a good idea to give the child paracetamol and after 45 minutes give it a little to drink and eat. Paracetamol kills the pain so that the child can drink.

What can you do?

It is important to begin the treatment as quickly as possible. Therefore, it is wise to keep some crème at home, if the child has had its first outbreak of cold sores, ready for immediate treatment – in the case of a new outbreak.

Avoid the child picking at the cold sore – in part, this can spread the illness and, in part, it can lead to further bacterial inflammation.

Beware of getting infected. Wash your hands after touching the sores.

Contact the doctor tomorrow

At the first outbreak of a cold sore. If the sores have not healed in the course of 2 weeks. If the sores are watery with a thick goo. If the cold sores appear very frequently.

Contact the doctor immediately

If the sores spread to the nose or the eyes. If the child’s eye becomes red.