In short
Cold sores are caused by a contagious virus called herpes simplex virus (HSV).
What it is1
Cold sores are common and usually clear up on their own within 10 days.
NHS website
Worth knowing6
A cold sore usually starts with a tingling, itching or burning feeling.
NHS websiteOver the next 48 hours one or more painful blisters will appear on your face.
NHS websiteThe blisters burst and crust over into a scab.
NHS websiteCertain things may trigger a cold sore, such as illness, sunshine or being on your period.
NHS websiteCold 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.
NHS websiteThere is no cure for cold sores.
MedlinePlus
What helps4
Antiviral medicines can help them heal faster.
MedlinePlusA 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.
NHS websiteIf you regularly get cold sores, use antiviral creams as soon as you recognize the early tingling feeling.
NHS websiteUse sunblock lip balm (SPF 15 or above) if you are outside in the sun.
NHS website
What to avoid2
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.
NHS websiteDo not touch your cold sore, apart from applying antiviral cream, and wash your hands before and after if you do.
NHS website
See a provider if1
See a health care provider 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.
NHS website
Sources
- MedlinePlus, National Library of Medicine: Cold sore
- NHS website: Cold sore (adapted; Open Government Licence v3.0), as at 13 October 2026
Contains public sector information licensed under the Open Government Licence v3.0.
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