Cold sores

At a glance

  • Cold sores are painful blisters on or around the lips.
  • After a few days they scab over and heal.
  • They are caused by an infection with herpes viruses.
  • The blisters may keep coming back once you've been infected.
  • Creams and tablets can speed up the healing process somewhat.

Introduction

Photo of a man looking at his cold sore in the mirror
PantherMedia / Tomas Anderson

Many people will be familiar with that typical tingling or itching feeling around their lips that comes about one day before cold sore blisters and swelling appear. Although these typical symptoms are bothersome, they usually go away on their own within one to two weeks.

They are caused by a certain type of contagious herpes . Many people have these viruses in their body, but they don’t always lead to cold sores. Those who have had a cold sore in the past will often keep on getting them, though.

Symptoms

Cold sores (herpes labialis) cause a patch of skin around the upper or lower lip to itch or tingle. The skin tightens up and reddens, and painful blisters start to form. They can also spread to the surrounding skin, the mouth or towards the nose.

Illustration: Cold sores, from left to right: Redness, blisters, crusting – as described in the article

Cold sores, from left to right: Redness, blisters, crusting

The blisters easily break open when you talk, laugh or chew. They then ooze fluid. Acidic foods and drinks like juice or vinegar can irritate the wound. When the wound heals, it crusts over into a scab.

Cold sores are often more unpleasant the first time you get them – most commonly as a young child – because your body doesn’t yet have any antibodies against the virus. They may then cause symptoms such as a fever, weakness and swollen lymph nodes in the neck area. The lining of their mouth may become severely inflamed and hurt, too. This leads to bad breath.

Causes

Cold sores are caused by herpes simplex viruses. There are two types of herpes simplex viruses, known as type 1 and type 2. Cold sores are usually caused by herpes simplex type 1. The type 2 herpes simplex causes genital herpes. The herpes is spread through the fluid in the blisters or open sores, for instance through kissing, but also through objects or fingers that touch your mouth. It can also be spread during oral sex. The viruses may be passed on from your mouth to a sexual partner's genital area. Type 1 herpes viruses can also cause genital herpes this way.

The viruses live in a cluster of nerve cells (ganglion) at the side of the face, known as the trigeminal ganglion. If you become infected with herpes viruses, they stay in your trigeminal ganglion for the rest of your life. People get a cold sore if the viruses move along the nerves to the lips, where they cause the typical symptoms.

The blisters mainly appear when the is weakened or under strain, possibly because of a cold or fever. Physical strain, stress and hormonal fluctuations are also thought to be possible triggers, as well as skin irritation around the lips due to sunlight or intense kissing, for example. But it still isn’t clear why some people keep getting cold sores and others don’t.

Prevalence

It is estimated that about 60 to 90% of all people in Germany are carriers of the herpes simplex type 1. The likelihood of having the in your body increases with age. A lot of people aren’t aware that they have it because they don’t have any symptoms. It is thought that an ends up leading to cold sores in about 20 to 40% of people who have the .

Outlook

Many people can already feel their lip tingling or itching several hours or a day before visible blisters form. While the sores are healing, they may crust over into scabs, which can also easily crack and bleed.

It takes about one to two weeks for cold sores to go away. The small wounds don’t leave any visible scars.

Some people keep on getting cold sores – usually one to two times per year. But about 5 to 10% of people who get them have more than five per year. The symptoms often become less severe over time, though.

Effects

In people who are otherwise healthy, cold sores go away on their own without any long-term health consequences.

If someone has a skin condition like or severe burns, the herpes can infect larger areas of skin. This rarely happens, though. In rare cases, the can also cause eye infections. Then herpes blisters develop on your eyelids, for example. If the is affected, your eyes water and turn red, and your vision may be impaired.

In people who have a very weak immune system, for instance due to chemotherapy to treat cancer, the can take longer to go away, be more severe and sometimes lead to complications.

Diagnosis

Cold sores can be easily diagnosed based on the typical symptoms. Most people who have had a cold sore in the past know that they’re getting another cold sore as soon as they notice the first signs. It usually isn’t necessary to go to a doctor unless something unusual happens.

In rare cases, the herpes occurs in skin elsewhere on the body. The doctor can then take a sample of fluid from the blisters and have it tested for herpes viruses in a laboratory.

Prevention

People usually become infected with herpes viruses in early childhood. That is why it's not especially important for adults to take special measures to protect themselves from a first . It is more important to protect others from being infected.

Generally speaking, until the cold sore blisters and scabs have completely gone away you can protect other people from by

  • not kissing anyone,
  • not sharing towels, dishes and cutlery,
  • washing your hands if you touch your lips with them (for example, after putting on cream),
  • avoiding sports that involve physical contact, and
  • avoiding oral sex. The herpes can spread from the lips to the membranes lining the genitals, leading to genital herpes.

Newborn babies under the age of 8 weeks are particularly at risk because their hasn’t had time to develop. People who have a cold sore should take care not to kiss the baby or put the baby’s pacifier in their own mouth. They should also wash their hands regularly and make sure that the baby doesn't accidentally touch their cold sore.

In theory, people can pass the cold sore on to others even if they don’t have a cold sore at the time. This very rarely happens, though, so there’s no need to take any precautions if you don't currently have a cold sore.

There are also some preventive steps you can take to reduce the number of outbreaks. People who have noticed that the symptoms are more common after certain situations like sunbathing can try to avoid those triggers or protect themselves: Sunscreen and good lip care could help, for instance.

People who get cold sores very frequently are sometimes advised to take medication to try to prevent them. But there is hardly any research on how effective this medication is.

Treatment

Cold sores clear up on their own, so there’s usually no need for treatment.

Antiviral ointments, creams, patches or gels can speed up the healing process of an acute outbreak by about one day. Sometimes they can prevent blisters and scabs from forming too. They contain the drugs acyclovir or penciclovir, and are available from pharmacies without a prescription.

It’s important to use them correctly: In order for the treatment to be able to work, it has to be started within 24 hours of the first symptoms arising. The sooner you start it, the better. The antiviral medications are then applied thinly to the affected area every 2 to 3 hours, over a period of five days.

Unlike creams and other topical (external) treatments, antiviral tablets are only available on prescription. These tablets can also speed up the healing process by about one day. It’s not clear whether they are more effective than topical treatments. But they are easier to use because you only need to take them once or twice a day.

The protective effect of tablets is much greater in people who have a weak , for instance during chemotherapy.

Everyday life

Most people who get cold sores now and then don't feel that it really affects their everyday life. People who have cold sores don’t have to stay home from work or school. But the symptoms can be distressing, and it can be hard work to make sure the is not passed on.

Some people are troubled by the cold sores being visible. They feel less attractive because of the cold sore and tend to keep to themselves during an outbreak. But a lot of people don't notice when other people have a cold sore, or at least don't think badly of others because they know the problem themselves.

Some cold sore creams are available with pigments. At least for people with fair skin, they can conceal the reddening a little. It is worth remembering that the viruses can easily be spread by the fingers or make-up brushes if you use make-up. Covering the cold sore with make-up could also interfere with the healing process by breaking the blisters and scabs when applying make-up, or because of other germs entering the sores.

Small cold sore patches are available to protect the affected areas of skin. But hygiene and caution are important here, too. The softened scabs can peel off and bleed when the patches are removed.

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

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Updated on March 23, 2022
Next planned update: 2025

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Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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