The herpes virus that causes cold sores predominantly affects the inside of the mouth, lips, and the areas of skin around the mouth, nose, and eyes. Initial infection usually passes unnoticed, though it can occasionally cause: malaise, sore throat, enlarged lymph glands and widespread ulceration of the mouth the whole of the oral mucosa may be bright red and sore; this is most commonly seen in children, and is called herpetic stomatitis. A slow recovery takes place over a period of about 10 days. However the virus is not completely eliminated from the body, and remains in a latent form which, when reactivated, is responsible for the production of cold sores.

Cold sores are caused by a complex reaction involving the virus and the body's own defence system. Some individuals find that the condition may be triggered by exposure of the face to strong sunlight, although other factors such as cold temperatures, stress, menstruation, and any debilitating condition may also be important. Patients having dental treatment may be prone to cold sore, particularly if their lips are dry, treatment has been long and difficult, and if they also run down. The most common location for a cold sore is on the lip.

If an association between sunlight and cold sores has been observed, then the most sensible precaution is to keep out of the sun, and to wear a hat or sunshade; sun-blocking preparations on the lips and face are essential.

Typically, arrival of the lesion is preceded by a period of itching and irritation over the affected area. Within a few hours, blisters appear and these then burst and form a scab. Healing takes place over a period of about 10 days.

Be particularly careful not to touch the cold sore with the fingers and then rub the eyes. An infection of the finger end around the nails is possible, or worse, a serious infection of the surface of the eye. Do not kiss while you have a cold sore and especially avoid kissing children who may as a result develop herpetic stomatitis (see above).

We like to give patients who frequently suffer from cold sores a prescription for the anti-viral agent acyclovir (Zovirax). The cream should be applied to the affected area, and can shorten the duration of an outbreak considerably, especially when used immediately the first symptoms are recognised.