Cold Sore Treatment

£19.99 Includes free private prescription
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Valaciclovir 500mg

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Cold Sores

What are cold sores?

Cold sores are small fluid filled blisters that appear on parts of the face, usually around the lips and mouth. Cold sores have several typical stages of progression:

  • Stage 1 -you will feel a tingling, itching or burning feeling

  • Stage 2 -small fluid filled blister(s) appear

  • Stage 3 -blisters will burst and scab over

  • Stage 4 -scabs will slowly heal until the cold sore is no longer visible

For most people, cold sores will begin to heal within ten days and often don’t require treatment. For some people, cold sores can be bigger than normal or take longer to heal than expected, in these cases it may be appropriate to seek treatment.

How do you catch cold sores?

Cold sores are caused by a virus called the herpes simplex virus (HSV). This virus is very common, in 2012 it was estimated that 67% of the world’s population were infected with this virus. The virus is caught by coming into contact with other people with an active infection. This is often during childhood when children come into close contact through activities such as play.

For most of your life, the virus will lie dormant in your skin, suppressed by your immune system. Occasionally the virus will reactivate causing a cold sore. This is often when your immune system is temporarily weakened, by example through stress or illness.

As cold sores are caused by a viral infection which currently can’t be cured, many people will experience repeated cold sores. This is because the virus repeats the cycle of reactivation over and over again.

When are cold sores contagious?

Cold sores are contagious as soon as you feel a tingling, itching or burning sensation on your face, until the blister has burst, scabbed over and fully healed.

If you or your child has a cold sore, it is a good idea to avoid sharing eating utensils, drinking bottles or other items that regularly come into contact with your mouth and face. You should also avoid touching the cold sore directly and regularly wash your hands – this will help prevent the virus from being passed from one person to another.

Cold sores and genital herpes

The virus which causes cold sores can also be transmitted to the genitals and anus, potentially causing genital herpes, but this is not as common. If you are worried, you should avoid touching your cold sores with your hands, regularly wash your hands and consider treating your cold sore with an oral medicine or cream.

You should not engage in oral sex while you have a cold sore as this can increase the risk of passing the virus to a partner. You should also use a condom during sex as this can reduce your risk of contracting or passing on HSV infection of the genitals.

When do cold sores need treatment?

Most cold sores will not require treatment and cold sores are very common, particularly in children.

However, some people may experience particularly large, painful or prolonged cold sores and in these scenarios, treatment may be appropriate. Treatment can be discussed with your GP, Pharmacist or accessed online through a registered online Doctor and Pharmacy service such as MedExpress.

What is Valaciclovir?

Valaciclovir is an antiviral medicine. It stops the infecting virus from reproducing. Since the virus reproduces very early in the infection, you will benefit most from treatment if you take Valaciclovir Tablets as soon as the first symptoms appear, ideally within 5 days of their appearance.

Valaciclovir Tablets are used to treat Herpes simplex severe infections as they require a systemic antiviral #drug and they are licensed for the treatment of herpes simplex infections of the skin and mucous membranes causing herpes labialis (cold sores).

How to take Valaciclovir?

In order to treat Cold sores the regime is 2000 mg (4 tabs of 500 mg each) twice a day for one day only. The second dose should be taken about 12 hours after the first dose. You should remain well hydrated while you are taking Valaciclovir.

Do I need medical advice before taking Valaciclovir?

If you are elderly, renally impaired (damaged kidneys/reduced kidney function), pregnant or breastfeeding, you should seek medical advice before taking Valaciclovir.

If you have a damaged or weakened immune system (immunocompromised) you should seek medical advice before taking Valaciclovir and at any time you experience a cold sore or other infection.

What is the difference between Aciclovir and Valaciclovir?

Aciclovir and Valaciclovir are closely related. Valaciclovir is a pro-drug of aciclovir which means that after it is taken, it is converted in the body to aciclovir. The advantage of taking valaciclovir over aciclovir is that it doesn’t have to be taken as frequently as so it is more convenient for the patient to comply with the regime.

What is the difference between Valtrex and Valaciclovir?

Valaciclovir is the active ingredient in Valtrex and is available in a generic, unbranded tablet. Valaciclovir and Valtrex are medically equivalent but Valaciclovir is available at a much lower cost.

Generic medicines contain the same active ingredient and are equally effective and medically equivalent as the branded products but are available at a lower price. Generic manufacturers have to demonstrate that they are medically identical to the branded product - i.e. they offer the same quality, strength, stability and effectiveness.

Generic medicines are required to meet the same standards of safety, quality and efficacy as the branded medication. To receive market approval from the European Medicines Agency and MHRA, a generic medicine must be 'bioequivalent' to the originator product.

Side effects

As with all medicines, Valaciclovir should only be taken after carefully weighing the potential positives and negatives in conjunction with a qualified healthcare professional. The most common adverse reactions (ARs) reported by patients treated with Valaciclovir were headache and nausea.

The following side effects have also been reported:

Common (affects less than 1 in 10 patients receiving the medicine):

  • Feeling sick
  • Dizziness
  • Vomiting
  • Diarrhoea
  • Skin reaction after exposure to sunlight (photosensitivity)
  • Rash


Cold sores are common and for most people they will naturally heal and disappear after approximately ten days. You should carefully consider whether you need treatment, noting that treatment will have little or no effect unless used as early as possible.

Antiviral creams containing aciclovir and penciclovir, non-antiviral creams and cold sore patches are available in most chemists as over the counter options.

Additional steps you can do yourself:

  • eat cool, soft foods
  • use an antiseptic mouthwash if it hurts to brush your teeth
  • wash your hands with soap and water before and after applying cream
  • avoid anything that triggers your cold sores
  • use sunblock lip balm (SPF 15 or above) if sunshine is the trigger
  • take paracetamol or ibuprofen to ease pain and swelling (liquid paracetamol is available for children)
  • drink plenty of fluids to avoid dehydration
  • wash your hands with soap and water before and after applying cream

And always remember:

Do not kiss babies if you have a cold sore. It can lead to neonatal herpes, which is very dangerous to newborn babies.

Find out more about cold sores and alternatives to treatment here.

Information Leaflet

Patient Information Leaflet

Always read the patient information leaflet before commencing treatment. View patient information leaflet.

Authored 02 April 2020 by Dr Clare Morrison, Reviewed 02 April 2020 by Liyya Patel, Siobhan Titre Last updated 02 April 2020

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How our service works

It’s quick, easy, and safe to order from MedExpress — your fully regulated, London, United Kingdom based online pharmacy.

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Start a free 2 minutes online consultation with simple questions about your health.


Our UK medical team will then recommend a treatment and issue a free prescription.


Your treatment will be sent direct from our London pharmacy in discreet packaging.

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Our qualified team

All our doctors and pharmacists are based in the UK and are registered with the General Medical Council and General Pharmaceutical Council.

Dr Clare Morrison

General Practitioner (Prescriber)
GMC: 3441561

Avnish Patel

GPhC: 2079950

Liyya Patel

Superintendent Pharmacist
GPhC: 2083287

Choosing Generic vs Branded Valaciclovir


Generic medicines contain the same active ingredient and are equally effective and equivalent as the branded products but are available at a lower price. Generic manufacturers have to demonstrate that they are medically identical to the branded product before they can be sold - i.e. they offer the same quality, strength, stability and effectiveness.