Herpes labialis

Herpes labialis, also known as cold sores, is a common viral infection. It is caused by a DNA virus known as herpes simplex type 1. It presents as water-filled blisters on and around the lips. Other sites where it can occur are the gums, tongue, roof of the mouth, inside of the cheeks, the nose, or elsewhere on the body. At first it may just make the skin tingle, itch, sting or burn. It can occasionally cause fever, muscle pain and swollen lymph nodes.

After infection there can be two stages. In the primary infection, grouped blisters appear localised to one area, such as the lips and around them. The first episode is often severe, because the body does not yet have antibodies against the virus; the commonest triggers are fever and cold. Recurrences can then occur at intervals varying from weeks to months and are usually milder than the first episode. They are due to reactivation of the virus, often triggered by a cold, a cough, excessive sun exposure, fever, fatigue and hormonal changes such as menstruation.

Herpes labialis is diagnosed by clinical examination by the doctor, from its typical appearance. Antibodies against the virus can also be detected in blood samples.

Mild cases are treated with an antiviral ointment applied to the area. In severe cases the doctor may prescribe an oral antiviral such as acyclovir or valacyclovir, usually for about a week. Frequent recurrences of cold sores may require longer-term treatment. Take whatever is prescribed exactly as your doctor directs.