Cold sores are caused by a virus called herpes simplex. (Herpes simplex viruses also cause genital herpes.) Most adults worldwide have been infected with this virus, usually when we were children and were kissed by someone with a tiny cold sore that they were not aware of. When a child first gets the infection, there may be no symptoms at all, or there may be a fever and a sore mouth that clears up after 2–3 weeks.
After the first infection, the virus often remains. We seem to have difficulty in getting rid of it completely. It travels away from the mouth using the nerves of the face as a pathway. When it reaches the clusters of cells at the end of the nerves (which are called ganglia), it stops. The herpes virus DNA then remains quietly in the ganglia. Fortunately, it does not damage the nerves or interfere with their function.
In some people (about 1 in 12), from time to time, the herpes virus travels back the way it came, along the nerve towards the mouth. This is called activation. But instead of going to the inside of the mouth, it takes a slightly different path and ends up in the skin of the lips or nearby. When it arrives in the skin, it causes a cold sore.
After the cold sore heals, the virus goes back up the nerve to the ganglion again, where it rests. But it can become activated again at any time, and travel down the nerves to the skin to cause another sore. The virus always travels up and down the same or nearby nerve pathways, which explains why cold sores always recur in roughly the same place.
Infection with herpes simplex virus causes sore mouth (or no symptoms)
Herpes virus travels up nerves to the nerve ganglion where it remains
At a later date, herpes virus may travel down the nerves to the skin, causing a cold sore
The cold sore heals, and herpes virus retreats to the ganglion again
At a later date, herpes virus may travel down to the skin again, causing another cold sore (recurrence)
What activates the virus to cause a cold sore? No-one really understands why the virus in the ganglion suddenly wakes up from time to time, and decides to go to the skin and cause a cold sore. But, in some people, there are some definite triggers that make this happen, such as:
other damage to the skin
physical stress, such as having another illness
major dentistry, such as having a tooth out
Preventing another attack
Keep out of wind as much as possible. If you ride a bike, wrap a scarf around the lower part of your face.
Use sunblock if you find sunshine provokes an attack. This really can work. Researchers tried it out on 38 people who suffered from recurrent cold sores and it stopped the problem. Then they supplied a fake sunscreen, and 71% of the people developed a cold sore. (This research was published in The Lancet in 1991.)
Choose a high-factor sunblock (such as those intended for skiers), and apply it to the area where your cold sores occur. Don’t just dab on the exact spot – cover the surrounding skin also, because cold sores don’t always recur in exactly the same spot. If you tend to get sores on the actual lip, use a lip balm that contains UV protection.
Don’t waste money on special supplements. Some people think that taking a supplement of L-lysine (an amino acid) will prevent cold sores, or will help your cold sore heal rapidly. There is no scientific evidence that this works.
Eat healthily and don’t exclude foods from your diet. Some people think that avoiding foods that are high in arginine (an amino acid) or low in L-lysine will help to prevent attacks. Therefore they avoid wholegrains, nuts, onions, green vegetables, coconut and chocolate. The problem is that all these foods form part of a healthy diet (yes, even chocolate), and there is no scientific evidence that cutting them out has any effect on herpes.
It makes sense to keep generally healthy, and this means eating a varied diet with plenty of fruit and vegetables and iron-containing foods. Although there is no scientific evidence for its benefits, there would be no harm in trying a diet that is high in L-lysine. Such foods include yoghurt, apples, pears, mangoes, tomatoes, beetroot, chicken and oily fish.
Avoid stress is a common piece of advice to cold sore sufferers. It is true that cold sores do tend to occur when people are run-down or stressed, but avoiding stress is more easily said than done.
See your doctor if you are having really bad or frequent attacks, or if you also have eczema or other health problems. Your doctor might consider prescribing an antiviral drug in tablet form as a preventive measure, or giving you a supply of tablets to take at the first sign of another attack