This factsheet is for people who have cold sores, or who would like information about them.
Cold sores are small, fluid-filled blisters that develop around the lips or inside the mouth. They are caused by the herpes simplex virus (HSV), which is passed on through skin-to-skin contact such as kissing.
There are two types of HSV – HSV-1 and HSV-2. Most cold sores are caused by HSV-1, whereas most genital sores (genital herpes) are caused by HSV-2. Both types of HSV can cause sores to develop on your face or genitals.
From the first time you get HSV, which is known as the primary infection, it stays in your body for the rest of your life. About eight in 10 people have HSV.
The primary HSV infection can develop in different ways. It may cause mild symptoms or no symptoms at all. Children under five are most likely to feel unwell from the primary infection. For example, your child may have:
The blisters inside your child’s mouth usually appear between one and three weeks after he or she gets the virus. They can sometimes take up to three weeks to heal.
In adults, the primary infection may cause a glandular fever-type illness, with symptoms such as a sore throat, swollen tonsils, fever and headache.
After you have had the primary infection (with or without symptoms), the virus lies dormant (inactive) in your body. It moves into your nerve cells, but can become active again. This is known as a recurrent infection and causes blisters to develop on your lips. These blisters are commonly called cold sores and usually heal within five to 10 days.
A cold sore outbreak usually starts with a tingling sensation, redness and swelling around your lip. Then, small, fluid-filled blisters form, which break open and develop a yellow crust (scab). The scab usually falls off around seven days later. Recurrent outbreaks usually occur in or around the same place each time. It's possible to have several a year.
You probably won’t need to see your GP if you have these symptoms as you can usually manage them at home. However, if they get worse, don’t improve within seven days, or you have recurrent outbreaks, see your GP for advice.
Complications of cold sores can include the following.
If you have symptoms of either primary or recurrent HSV infection and you have a weakened immune system (if you have HIV/AIDS or are taking medicines that suppress your immune system), you should see your GP. This is because there is a risk that the virus may cause a serious illness.
Although rare in the UK, there is a risk that women can pass the HSV infection to your baby in pregnancy, during the birth or immediately after birth. This is known as neonatal herpes and can cause your baby to be seriously ill. This is more of a problem if you have genital herpes. If you have any symptoms of a primary HSV infection or cold sores for the first time when you are pregnant (particularly in the later stages of pregnancy), you should see your GP or obstetrician for advice.
Cold sores are usually caused by HSV-1. The infection is passed on through skin-to-skin contact, for example by kissing someone who has the virus or by sharing objects that have been in contact with the virus, such as a razor or a lipstick.
There are several factors that can trigger cold sores, including:
For many people, however, the trigger is unknown.
Usually, your GP will be able to recognise cold sores by looking inside and around your mouth. He or she may take a swab from the blister and send it to a laboratory to be tested. This is to confirm that the infection has been caused by HSV.
Treatment for cold sores usually involves self-help measures to ease your symptoms. There isn’t a treatment that can get rid of HSV. Once you’re infected, it will remain in your body even if you never get any symptoms.
An over-the-counter antiviral cream can help cold sores clear up more quickly, particularly if you apply it when you first notice the symptoms. If you have any pain or discomfort, you can take over-the-counter painkillers, such as paracetamol or ibuprofen. Children can take liquid painkillers. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.
If you (or your child) have severe blistering in your mouth and gums, the following steps may help ease any pain or discomfort.
If the infection is particularly severe, or frequent, your GP may prescribe a treatment, such as:
Always ask your GP for advice and read the patient information leaflet that comes with your medicine.
If you have cold sores, there are steps you can take to help stop them spreading to other parts of your body and to other people. Some examples are listed below.
There are also some measures you can take to prevent yourself getting cold sores. Some examples are listed below.
Stress and feeling run down can trigger recurrent episodes of cold sores. Taking measures to prevent yourself feeling this way can also help reduce your risk of having an outbreak.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.
Produced by Krysta Munford, Bupa Health Information Team, January 2012.
Compare Bupa's range of health assessments, designed to help you understand and manage your health. Call 0845 600 3458 and quote ref. HFS100 to find out more.
Bupa Health Finder
Find health information and more while on the move with our free Bupa Health Finder app.