A cold sore usually starts with a tingling, itching or burning feeling.
Over the next 48 hours one or more painful blisters will appear on your face.
Cold sores are contagious from the moment you first feel tingling or other signs of a cold sore coming on to when the cold sore has completely healed.
They can easily spread to other people and other parts of your body.
To help stop cold sores spreading:
- wash your hands with soap and water whenever you touch your cold sore
- do not kiss anyone while you have a cold sore
- do not have oral sex until your cold sore completely heals as you could give your partner genital herpes
A pharmacist can recommend:
- creams to ease pain and irritation
- antiviral creams to speed up healing time
- cold sore patches to protect the skin while it heals
You can buy electronic devices from pharmacies that treat cold sores with light or lasers.
You may find these helpful, but there's not much evidence to confirm they work.
There are things you can do to help ease cold sores while they heal and to avoid triggering a cold sore.
See a GP if:
- a cold sore has not started to heal within 10 days
- you're worried about a cold sore or think it's something else
- the cold sore is very large or painful
- you or your child also have swollen, painful gums and sores in the mouth (gingivostomatitis)
- you have a weakened immune system – for example, because of chemotherapy or diabetes
A GP may prescribe antiviral tablets if your cold sores are very large, painful or keep coming back.
Newborn babies, pregnant women and people with a weakened immune system may be referred to hospital for advice or treatment.
Cold sores are caused by a virus called herpes simplex.
Most people are exposed to the virus when they're children after close skin to skin contact, such as kissing, with someone who has a cold sore.
Once you have the virus, it stays in your skin for the rest of your life. Sometimes it causes a cold sore.