What you need to know

Cold sores are proof that life can be unfair. Some people get them, others don’t. Besides being itchy and painful, cold sores make you feel self-conscious. They usually clear up without treatment after 7-10 days, but treatments can help shorten cold sore attacks, when used at the first sign of an outbreak. Use this slideshow to help recognise, prevent and treat cold sores.

Don't blame your cold

Cold sores aren't caused by the common cold. They're caused by the herpes simplex virus (HSV), passed on through contact with infected skin or body fluid. There are two types of HSV, type 1 and type 2. Cold sores are usually caused by type 1, but can also be caused by type 2. HSV damages the skin as it reproduces itself, creating cold sores that last about a week. Between outbreaks, HSV hides out inside nerve cells, so it's never completely cured.

Who gets cold sores and why

More than half of us have been infected with the HSV-1 virus, usually from well-meaning kisses from relatives or romantic partners. So why do only an unlucky few get cold sores? The answer may be in your genes. One study identified 6 genes that many people with cold sores share. Three of those genes may relate to how HSV-1 reactivates itself, causing outbreaks.

Stress can trigger a cold sore

HSV spends most of its time inactive, hiding in nerves. Many people have familiar triggers that tend to bring HSV out of seclusion, causing cold sores. Sunlight, fever, stress and menstruation are common triggers. Some people get cold sores twice a year; for others, it's a frustrating, stressful, monthly ritual.

Mouth ulcers and cold sores aren't the same

Cold sores usually appear on the lip, but can appear elsewhere on the face, for example around the nose. Mouth ulcers affect the inside of the mouth. Mouth ulcers don’t involve the herpes virus, and aren’t contagious. No one knows what causes them. Cold sores generally announce their arrival with a warning period of red, irritated skin. Blisters form, rupture, then crust over before healing.

When you're contagious

A cold sore is caused by skin damage as the herpes virus reproduces itself within infected cells. From the time skin turns itchy or red, HSV is likely present and can be spread. Cold sores are most contagious when blisters are present and just after they rupture, until the skin is completely healed and looks normal again. However, some people can transmit the virus from skin at any time, even if they haven’t got a cold sore.

How is the cold sore virus spread?

HSV usually spreads through skin-to-skin contact. The cold sore virus is usually present on an infected person's lip, even if there's no obvious sore. So the main way it is transmitted is by kissing. Objects that come into contact with the infected area, such as cutlery, can potentially pass on the infection. Oral sex by someone with a cold sore can lead to HSV infection of the partner's genitals. If a person has genital HSV and receives oral sex the person performing oral sex may develop cold sores.

How to avoid spreading the virus

Use caution while a sore is present: No kissing, no sharing of toothbrushes, tableware or glasses, and no oral sex. That will reduce most spread of HSV, although you may not be able to entirely eliminate the possibility of it spreading.

Easing cold sore pain

While the initial outbreak can last up to 2 weeks, recurrent outbreaks usually last about a week. Some people may find relief with hot or cold compresses. There is no cure for cold sores, but some over-the-counter creams and gels can provide relief from the symptoms of burning and pain.

Using antiviral creams and other treatment

Antiviral creams can reduce the time it takes a cold sore to heal if applied at the very first sign of a cold sore. These are available from pharmacies without a prescription. Used as directed, they can speed up the healing time of recurring cold sores. Cold sore hydrocolloid gel patches may also be recommended to promote healing while hiding the cold sore. Painkilling creams and medication may also help.

Prescription cold sore medications

Tablets on prescription can also reduce the amount of healing time, when taken at the first sign of a cold sore, for example, having red or itchy skin. Dosage and effectiveness vary, and your GP can recommend an appropriate treatment for you.

Is this a cold sore?

What about a cold sore that's not on your lip? They are not as common, but cold sores can appear anywhere around the mouth, nose or elsewhere on the face. Most people's cold sores reappear in the same area each time.

Can you spread it on your body?

It's possible, though rare, to spread the cold sore virus from one part of the body to another. It can happen by touching a cold sore, then touching an area of broken skin or a mucous membrane - the moist protective lining of skin found in areas like the eyes or vagina. That can lead to a herpes skin infection. This self-spreading can be prevented by washing hands and not touching the cold sore.

When herpes infects the fingers or eyes

Among the other areas the cold sore virus can infect are the finger, called herpetic whitlow, and the eye, called ocular herpes. Ocular herpes most often occurs on the cornea and left untreated can cause loss of sight. Herpetic whitlow can be painful, and children can get this by spreading the virus from a cold sore by sucking fingers or thumbs.

Preventing outbreaks

It can be hard to prevent cold sores entirely, but reducing your triggers can help. Stay out of the sun, or use sunscreen and UV-blocking lip balm. Learn and practise stress management strategies that work for you. Keep your immune system healthy by getting plenty of sleep and regular exercise.

When to seek medical advice

If you have severe or frequent cold sore outbreaks, you should seek medical advice. You may benefit from taking daily suppressive antiviral medication to help reduce the frequency of cold sores.

Related reading

• More about cold sores
• Cysts, lumps and bumps
• What's that rash?
• Moles, freckles and skin tags
• Mouth ulcers
• Blisters