Diseases & care
Cold sores explained
Cold sores are small blisters that appear around the lips and mouth, and most people have had one at some point. They are caused by a very common virus and, while they can be sore and annoying, they usually clear up on their own within a couple of weeks. They do tend to come back, often at inconvenient times. This guide explains, in plain terms, what cold sores are, why they keep returning, how to treat and soothe them, how to avoid passing them on, and the situations where you should seek medical advice.
Education and reference only. This article explains how treatments work in plain language — it contains no doses and is not a substitute for advice from your doctor or pharmacist. Always discuss your own treatment with a qualified clinician.
What causes cold sores
Cold sores are caused by the herpes simplex virus, usually type 1. This virus is extremely common and most people catch it in childhood, often from a kiss from someone who carries it, frequently without ever knowing. Once you have the virus, it stays in your body for life, resting quietly in the nerves near where the cold sore appears. Most of the time it causes no problems at all. From time to time it can reactivate and travel back to the skin, producing a cold sore. This is why cold sores tend to appear in the same spot and keep coming back. Carrying the virus is normal and very widespread, and it does not mean you have done anything wrong.
Recognising a cold sore and its triggers
A cold sore often starts with a tingling, itching or burning feeling around the lip a day or so before anything appears. Small fluid-filled blisters then form, usually in a patch, which soon burst, weep and crust over into a scab before healing. The whole cycle typically takes around ten days to two weeks. Common triggers that can reactivate the virus include being run down or unwell, having a cold or fever, tiredness and stress, strong sunlight, and, for some women, their monthly period. Not everyone has an obvious trigger. Recognising the early tingling stage is useful, because starting treatment then gives the best chance of easing the outbreak or shortening it.
Treating and soothing cold sores
Most cold sores heal on their own without treatment. Antiviral creams from a pharmacy can help if started as soon as you feel the early tingling, before blisters fully form, though they only modestly shorten an outbreak. Cold sore patches can cover the sore, protect it and help it heal. Simple painkillers such as paracetamol or ibuprofen can ease soreness if needed. To soothe the area, avoid picking or squeezing the blisters, keep it clean, and use a lip balm to stop it drying and cracking. Very frequent or severe cold sores may need antiviral tablets, which a doctor can consider. A pharmacist is a good first port of call for advice on suitable treatments.
Stopping cold sores spreading
Cold sores are most contagious when the blisters are weeping, but the virus can spread at other times too. To avoid passing it on, do not kiss anyone while you have a cold sore, and especially avoid kissing or close contact with newborn babies, as the virus can make them seriously ill. Do not share items that touch your mouth, such as cups, cutlery, towels, lip balms or razors. Wash your hands after touching a cold sore, and try not to touch it, particularly to avoid spreading the virus to your eyes or to other people. Avoid oral sex while you have a cold sore, as the virus can be passed to the genitals. These simple steps greatly reduce the risk of spreading it.
When to get medical advice
Most cold sores need no medical attention, but seek advice in some situations. See a GP or pharmacist if a cold sore has not healed within about ten days to two weeks, is very large or painful, keeps coming back frequently, or if you get them often and they bother you. Get medical advice more urgently if you have a weakened immune system — for example from certain illnesses or treatments — as cold sores can be more serious. Cold sores near or in the eye, causing eye pain, redness or vision problems, need prompt medical assessment. If a baby under a few weeks old has a cold sore or seems unwell after contact, seek urgent medical help, as the virus can be dangerous for newborns.
In short
Key takeaways
- Cold sores are caused by the very common herpes simplex virus, which stays in the body for life and can reactivate.
- They often start with tingling, then form blisters that crust over, usually healing within about two weeks on their own.
- Antiviral creams work best if started at the first tingle; patches and simple painkillers can ease and protect the sore.
- The virus is contagious, so avoid kissing, sharing cups or towels, and especially avoid close contact with newborn babies.
- See a GP if a cold sore does not heal in two weeks, keeps returning, affects the eye, or if you have a weakened immune system.
Answers
Frequently asked questions
Will a cold sore ever go away for good?
The individual cold sore heals, usually within two weeks, but the virus stays in your body for life and can reactivate later, often in the same spot. There is no cure that removes the virus, but many people find outbreaks become less frequent over time, and treatments can ease and shorten them.
How do I stop passing a cold sore to others?
Avoid kissing and close contact while you have a cold sore, and do not share cups, cutlery, towels, lip balms or razors. Wash your hands after touching it. Take special care around newborn babies, as the virus can make them seriously ill, and avoid oral sex, which can pass it to the genitals.
When should I see a doctor about cold sores?
See a GP or pharmacist if a cold sore has not healed in about ten days to two weeks, is very large or painful, or keeps coming back. Get advice more urgently if the sore is near your eye, if you have a weakened immune system, or if a very young baby has been in contact and seems unwell.
Go deeper
Related guides
Sources
Where this is drawn from
- NHS — Cold sores.
- NICE CKS — Herpes simplex — oral.
- British Association of Dermatologists — Herpes simplex patient information.
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