“I have developed a small blister on my lower lip that my GP has told me is a cold sore. What is this?"
A cold sore is an infection caused by the virus herpes simplex. There are two kinds of herpes simplex viruses, type 1 causes the cold sores around the mouth, whilst type 2 causes genital herpes.
Cold sores are very common. Because the virus is very contagious, about 8 in 10 people in the UK have been infected with type 1 and about 1 in 4 with type 2. The type 1 virus can be passed between people by kissing, and infection is usually passed on in childhood.
Despite being so common, not everyone who carries the virus will get a cold sore. The immune system is not able to get rid of the virus because it tends to hide inside nerves where the immune cells are unable to get access. This means that at times of stress, during a period, exposure to sunlight, or infections, the virus can emerge and cause problems again. If you are prone to cold sores, it can help if things that precipitate an attack can be avoided. If you think you have a cold sore, then it is best to avoid kissing others until it has gone, and to avoid sharing lipstick, and eating and drinking utensils.
The symptoms of a cold sore start with a tingling at the site where it is due to appear. It then becomes a small spot that may last for a week or so before disappearing without a scar. Sometimes it may go on to become infected and develop into a small blister. In more severe cases, the condition can make you feel unwell with a fever and become painful.
The treatment for a cold sore is an ointment called acycloivir. This is available as an ointment over the counter at the chemists. It works by interfering with the DNA of the virus. It works best when it is applied as soon as the tingling starts, and can reduce the length of symptoms by about 20%. In more severe cases, your doctor may give you acyclovir tablets that have to be taken 5 times a day.
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