Cold sores are small, painful blisters that usually develop on or around the lips. They are caused by the herpes simplex virus, most commonly herpes simplex virus type 1 (HSV-1).

After someone is infected, the virus remains in the body and can become active again later. This means cold sores can return from time to time.

Many people first notice a tingling, burning or itching sensation before a blister appears.

Cold sores usually heal on their own within around 1 to 2 weeks, although some may take longer.

What Causes Cold Sores?

Cold sores are caused by the herpes simplex virus.

Once the virus enters the body, it stays inactive in nearby nerve cells. In some people, it may remain inactive for long periods. However, certain triggers can cause the virus to reactivate and produce another outbreak.

A cold sore does not necessarily mean that the infection was recently acquired. The virus may have been present in the body for months or years before an outbreak occurs.

HSV-1 and HSV-2

There are two main types of herpes simplex virus:

• HSV-1, which commonly causes cold sores around the mouth
• HSV-2, which more commonly causes genital herpes

However, either type can infect the mouth or genital area.

Cold sores around the lips are most often caused by HSV-1.

For more information about herpes infections, see our Herpes guide.

What Are the Symptoms of Cold Sores?

Cold sores often develop in several stages.

Tingling or Burning

Before the blister appears, you may notice:

• tingling
• itching
• burning
• tenderness
• mild pain

This is sometimes called the prodrome stage.

Starting antiviral treatment during this early stage may help reduce the severity or duration of an outbreak.

Blisters

Small fluid-filled blisters may then develop, commonly around the lips or mouth.

The surrounding skin may become:

• red
• swollen
• painful
• tender

Several small blisters may appear close together.

Oozing and Crusting

The blisters may burst and release fluid before drying out.

A crust or scab then forms over the affected area as the skin heals.

Avoid picking or scratching the sore, as this can irritate the skin and increase the risk of secondary infection.

Other Symptoms

A first herpes simplex infection can sometimes cause more general symptoms.

These may include:

• fever
• sore throat
• swollen glands
• tiredness
• headache
• pain inside the mouth
• swollen or sore gums
• reduced appetite

Recurrent cold sores are often milder than the first infection.

What Triggers Cold Sore Outbreaks?

Different people have different triggers.

Common triggers may include:

• stress
• tiredness or exhaustion
• illness or fever
• colds or flu
• strong sunlight
• wind or cold weather
• hormonal changes
• menstrual periods
• skin injury
• reduced immune function

Understanding your own triggers may help you reduce the frequency of outbreaks.

Are Cold Sores Contagious?

Yes. Cold sores are contagious and can spread through direct contact with the herpes simplex virus.

The risk of transmission is highest when blisters are present, particularly when they are open or weeping.

However, the virus can sometimes spread even when there is no visible cold sore.

How Are Cold Sores Spread?

The virus may be passed through:

• kissing
• oral sex
• direct skin-to-skin contact
• touching a cold sore and then touching another person
• sharing lip products
• sharing razors
• sharing toothbrushes
• sharing eating utensils or drinking containers

Avoid sharing personal items during an outbreak.

Cold Sores and Babies

Cold sores can be particularly dangerous for newborn babies because their immune systems are still developing.

If you have an active cold sore:

• do not kiss a newborn or young baby
• wash your hands before touching the baby
• avoid touching the sore
• keep the affected area covered where practical

Seek medical advice promptly if a newborn may have been exposed to herpes or develops blisters, fever, poor feeding or unusual drowsiness.

Cold Sore Treatment

There is no cure for the herpes simplex virus. However, treatment can help reduce symptoms and may shorten an outbreak.

Treatment works best when started as early as possible, ideally when tingling or burning first begins.

Antiviral Medicines

Antiviral medicines can reduce the ability of the virus to reproduce.

Depending on your circumstances, treatment may include antiviral creams or oral antiviral medicines.

Some oral antiviral treatments for recurrent cold sores may be available from a pharmacist following an assessment, while others require a prescription.

Your pharmacist can advise which treatment may be appropriate for you.

Do not use someone else’s antiviral medicine.

Pain and Discomfort

Simple measures may help relieve discomfort while the cold sore heals.

These can include:

• applying a cool compress
• using appropriate pain relief
• drinking cool fluids
• eating soft foods if the mouth is sore
• using a protective lip balm or petroleum-based product to prevent cracking

Speak with your pharmacist if you are unsure which products are suitable.

Cold Sore Patches

Cold sore patches can help protect the affected area.

They may also reduce touching and picking and provide a barrier over the blister while it heals.

Follow the product instructions carefully and wash your hands before and after applying a patch.

Should You Use Lysine?

Lysine supplements are sometimes promoted for preventing or treating cold sores.

However, evidence for their effectiveness is mixed.

If you are considering lysine or another complementary medicine, speak with your pharmacist first, particularly if you take prescription medicines, are pregnant or have a medical condition.

How to Prevent Cold Sore Outbreaks

It is not always possible to prevent outbreaks.

However, you may be able to reduce your risk by:

• identifying and avoiding personal triggers
• managing stress
• getting adequate rest
• protecting your lips from strong sunlight
• using SPF lip balm when outdoors
• eating a balanced diet
• managing other health conditions appropriately

People who experience frequent or severe outbreaks may sometimes be prescribed preventive antiviral treatment.

How to Avoid Spreading Cold Sores

During an outbreak:

• avoid kissing other people
• avoid oral sex
• avoid touching or picking the sore
• wash your hands if you touch the affected area
• do not share towels, toothbrushes or razors
• do not share lip balm, makeup, drinks or eating utensils
• avoid touching your eyes after touching the sore
• keep the area clean

Take particular care around babies and people with weakened immune systems.

Cold Sores and Oral Sex

HSV-1 can spread from the mouth to the genital area during oral sex.

Therefore, avoid oral sex while you have tingling, blisters, crusting or other signs of an active cold sore.

Barrier protection can reduce the risk of some sexually transmitted infections, but it may not completely prevent herpes transmission because the virus can be present on skin not covered by a condom or dental dam.

Cold Sores and the Eyes

Herpes simplex infection can occasionally affect the eye.

Avoid touching your eyes after touching a cold sore.

Seek urgent medical advice if you develop:

• eye pain
• redness
• light sensitivity
• blurred vision
• watering
• swelling around the eye

Herpes infection of the eye can be serious and requires prompt treatment.

For general information about eye symptoms, see our Eye Health guide.

Cold Sores and Eczema

Herpes simplex can sometimes cause a more serious skin infection in people with eczema.

If you or your child has eczema and develops rapidly spreading painful blisters, fever or feels unwell, seek urgent medical advice.

You can also read our Eczema guide.

When Should You See a Doctor?

Speak with a doctor if:

• the cold sore is very severe
• sores are not healing
• outbreaks occur very frequently
• the infection is spreading
• you have severe pain
• you have difficulty eating or drinking
• you develop signs of a bacterial infection
• you have a weakened immune system
• you are unsure whether the lesion is a cold sore

A doctor may recommend additional antiviral treatment or investigate other possible causes.

When Is Urgent Medical Care Needed?

Seek prompt medical attention if:

• a cold sore or herpes infection involves the eye
• a newborn baby may have been exposed
• a young baby develops blisters or appears unwell
• blisters spread rapidly over areas of eczema
• you are severely immunocompromised and develop a herpes outbreak
• you are unable to drink and are becoming dehydrated

Speak With Your Pharmacist

Your MediAdvice pharmacist can provide advice about cold sores and help you choose appropriate treatment.

Depending on your symptoms and health history, they may recommend:

• antiviral treatment
• pain relief
• protective cold sore patches
• lip care products
• medical assessment when needed

Starting treatment early can be helpful, so speak with your pharmacist when you first notice the familiar tingling or burning sensation.

General advice only: This information is not intended to replace advice from your healthcare professional. If symptoms are severe, persistent, spreading or concerning, seek professional medical advice.