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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.
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:
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.
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:
Symptoms are similar in adults, although you may also have bad breath (halitosis) and ulcers with yellow or grey centres in the mouth area.
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.
In the US and the UK, you can purchase antiviral creams for cold sores without a prescription. They are available 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 without prescription in the US and the UK. These cover the sore and can help it to heal.
To relieve pain and discomfort you may want to try non-antiviral creams, ibuprofen or paracetamol, although these treatments won’t encourage the cold sore to heal any faster.
Check what treatments are available without a prescription in your country.
Antiviral tablets prevent cold sores more effectively than antiviral creams. Your doctor may prescribe antiviral tablets if your cold sores are particularly large or painful, or if they keep recurring.
You should see your doctor for cold sores if:
Your doctor can prescribe medication for especially painful, large or frequent cold sores. 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.
Apart from buying cold sore medication, there are ways you can manage your symptoms and stop the infection from spreading. Try:
Do not give aspirin to children under the age of 16
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.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.