Cold sore

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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 virus. 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.


For many people, symptoms are more severe the first time they develop a cold sore. When you have a cold sore outbreak:

The first sign of a cold sore is usually a tingling, burning, or itching sensation on or around the lips, beginning about 12-24 hours before the cold sore develops.

The area becomes red, swollen and painful as the blisters form.

Over 2-3 days, the blisters rupture and ooze fluid that is clear or slightly yellow. This is sometimes called the “weeping phase.”

About 4-5 days after the cold sore appears, it crusts and scabs over. It might crack or bleed as it heals.

The scab then falls off, revealing skin that may be a little more pink or reddish than usual for a few days. It usually takes 1-2 weeks for the cold sore to heal completely.


Cold sores spread from person to person by close contact, such as kissing. They're usually caused by herpes simplex virus type 1 (HSV-1), and less commonly herpes simplex virus type 2 (HSV-2). Both of these viruses can affect your mouth or genitals and can be spread by oral sex.

Cold sores are sometimes called oral herpes because they are caused by the herpes simplex virus type 1 (HSV-1). This virus is very common and highly contagious. It spreads through saliva or close contact — often through kissing or by sharing utensils, straws, towels or lip balm with someone who has a cold sore.

You may not know if you have been infected with HSV-1 because symptoms of exposure to HSV-1 are generally mild. Children sometimes develop a fever and small blisters inside and around their mouths when they are first exposed to HSV-1.

Risk factors

Cold sore risk factors

infection, fever, or a cold.

sun exposure.


HIV/AIDS or a weakened immune system.


severe burns.



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In some people, the virus that causes cold sores can cause problems in other areas of the body, including:

Fingertips. Both HSV-1 and HSV-2 can be spread to the fingers. This type of infection is often referred to as herpes whitlow. Children who suck their thumbs may transfer the infection from their mouths to their thumbs.

Eyes. The virus can sometimes cause eye infection. Repeated infections can cause scarring and injury, which may lead to vision problems or loss of vision.

Widespread areas of skin. People who have a skin condition called atopic dermatitis (eczema) are at higher risk of cold sores spreading all across their bodies. This can become a medical emergency.


Certain things can activate the herpes virus. These include

UV rays (from natural sunlight or a tanning bed),

very hot or cold temperatures,

damaged or cracked lips, and

physical or emotional stress.

Avoiding these things may lower the risk of getting a cold sore. Sunscreen and good lip care might help too.

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.

Until the cold sore blisters and scabs have completely gone away, you can protect yourself and other people from infection 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 virus 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 immune system hasn’t had time to develop. Parents 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.

People who have cold sores don’t have to stay home from work or school.

Sometimes people pass the cold sore virus 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.