What is a cold sore?
Cold sores are small blisters or ulcers which appear on the mouth or the surrounding area. They are caused by a form of the herpes simplex virus (HSV-1), which, less commonly, can also cause genital herpes.
HSV-1 is very common: it affects around 67% of the world’s population under 50, according to the World Health Organisation (WHO). Once you have caught the infection, it stays in the body but remains dormant for the majority of time. This means you won’t always experience symptoms.
The virus can be activated by certain triggers, causing cold sores to develop. Not everyone responds to the same triggers, but they can include fatigue, illness, and sunshine. Some women tend to have more outbreaks around their period. It is possible to have the virus and never experience symptoms, or experience them very rarely.
There is no cure for HSV-1, but there are steps you can take to relieve pain, reduce outbreaks, and prevent the spread of infection.
Are cold sores contagious?
Cold sores can spread very easily through oral contact with sores, saliva, the inside of the mouth or the area around it. Less commonly, HSV-1 can spread through contact with the genitals of someone with a genital herpes infection.
A cold sore will become contagious as soon as an infected individual notices symptoms. This includes a tingling sensation where a cold sore is about to develop. They are most contagious when they rupture or burst. The sore will continue to be contagious until it has healed completely. This will usually take between seven and ten days.
It is possible to spread the infection without having any noticeable symptoms, but the risk of transmission is higher when an active sore is present.
If you have a cold sore outbreak and want to reduce the risk of passing the infection on, you should:
- only touch your cold sore to apply cream (dabbing it on gently rather than rubbing it in) and always wash your hands afterwards
- avoid sharing cold sore medications with others, particularly creams
- avoid sharing cutlery, lip products or anything else that comes into contact with the infected area
- avoid kissing or having sex, including oral sex, until your cold sores have healed completely
- take extra care when interacting with newborn babies, pregnant women, and individuals who have weakened immune systems (which can be caused by conditions like HIV or
Neonatal herpes is a dangerous condition that can occur in babies infected with the HSV virus. Young babies are more at risk from HSV as they do not have fully developed immune systems.
If you are pregnant and have a history of genital herpes or have recently contracted herpes, you should tell your doctor or midwife. They can offer treatments and advice that can help stop the virus spreading to your baby.
Cold sore symptoms
At the start of a cold sore outbreak, you may notice tingling, itching or burning on the affected skin. The cold sore may continue to develop over the next 48 hours, and will usually heal after about seven to ten days.
The small, fluid-filled blisters can appear anywhere on the face, but are common on the border of the lower lip. The blisters may burst and scab over, which is when they are most contagious.
You will not always develop a cold sore immediately after catching the infection. This is known as a primary infection. Children under five are more likely to experience symptoms in the primary infection than adults.
Symptoms of a HSV-1 primary infection in children include:
- excessive salivation
- a sore throat and swelling of the glands
- a high temperature or fever (38C)
- a headache
- herpes simplex gingivostomatitis - a condition which causes irritated, swollen gums and sores inside and around the mouth
Symptoms are similar in adults, although you may also have bad breath (
Recurrent infections are more common in adults than primary infections. Symptoms appear a while after the initial infection and may return in the future. These infections are less severe than primary infections and usually only cause cold sores and possibly swollen glands.
Many individuals are exposed to the HSV-1 infection when they are children, but they may not experience any symptoms until they are older.
Cold sore treatment
In the US and the UK, you can purchase antiviral creams for cold sores from most pharmacies. These creams aim to stop a cold sore outbreak at its onset. They won’t cure the HSV-1 virus or stop cold sores from coming back.
For the treatment to be effective, you must apply the cream to the affected area as soon as you notice any tingling, itching or burning. For the next four or five days, you will need to reapply the cream about five times a day.
You can also purchase cold sore patches in the US and the UK. These cover the sore and can help it to heal.
A doctor may advise taking painkillers such as paracetamol to relieve pain and discomfort, although these treatments won’t encourage the cold sore to heal any faster. Speak to your pharmacist or doctor for further guidance on whether to use these medications and how to get and use them.
Antiviral tablets prevent cold sores more effectively than antiviral creams. Your doctor may advise you to take antiviral tablets if your cold sores are particularly large or painful, or if they keep recurring.
When to see a doctor for cold sores
You should see your doctor for cold sores if:
- it has been ten days and the cold sore shows no signs of healing
- the cold sore is very large
- the cold sore is causing you a lot of pain
- you or a child in your care develops herpes simplex gingivostomatitis
- you are pregnant
- you have a weakened immune system (for example, due to a condition, treatment or medication)
- you are worried your cold sore is caused by something other than the HSV-1 virus
Your doctor may advise you take medication for especially painful, large or frequent cold sores. Speak to your pharmacist or doctor for further guidance on whether to use these medications and how to get and use them.
Individuals at greater risk from cold sores, like newborn babies or people with weakened immune systems, may be referred to a hospital for further support.
If your child is refusing to drink because of their symptoms, take them to their doctor or the nearest hospital emergency department.
How to get rid of a cold sore at home
Apart from buying cold sore medication, there are ways you can manage your symptoms and stop the infection from spreading. Try:
- eating foods that are cool and soft
- avoiding foods that are acidic or salty
- staying away from any cold sore triggers
- avoiding dehydration by drinking lots of fluids
- washing your hands thoroughly (using soap and water) if you touch the infected area
- only touching the infected area to apply cream
- applying an SPF of at least 15 to your lips if sunshine triggers your symptoms
Although it is not possible to cure the HSV-1 virus, there are self-help methods and medications available that can ease your symptoms, prevent the spread of infection, and minimise your cold sore outbreaks.
Seeing your doctor can be beneficial in some circumstances, like if you are pregnant or have a particularly large or painful cold sore. They can offer you further advice or stronger, more effective treatments.