Cold sores are small blisters around the mouth. They're common and affect around 70% of people.
Cold sores are caused by the herpes simplex virus (Type 1 herpes). Some people are at more risk of getting them than others and factors such as stress or tiredness can also increase your risk of getting them repeatedly. Sunshine can decrease your skin's immune response, so holidays in the sun may trigger them. And women may find that they're more prone to them during their period.
Many people find that a cold sore reappears in the same place on the lips or around the nose. They may also spread to other areas.
In some cases, they can affect the eyes. If this happens you will need emergency treatment to prevent damage to the eye and you should go to the hospital immediately.
If you have eczema, the spread of the herpes virus can be rapid and involve large areas of the body. This is also a medical emergency and you'll need to go to the hospital for treatment.
Treating cold sores
Cold sores usually disappear within a few days without needing treatment. But, you may want to try an antiviral cream such as acyclovir, which you can buy over the counter in pharmacies.
If you're particularly prone to cold sores triggered by the sun, then taking an oral antiviral tablet before going on a sunny holiday may help.
In repeated attacks, you may need to take an oral form of an antiviral such as acyclovir to prevent them recurring. This may mean taking the drug on a daily basis for many months and, in some cases, years.