Cold Sore Treatment (Mouth & Lips)

Cold sores are small painful blisters that usually occur on the face (lips, cheeks & nose). 

They are caused by the herpes simplex virus (HSV). This is a common virus and it is spread through direct skin-skin contact. It is very contagious. Most people are exposed to HSV during childhood (after kisses from a family member with the virus) and it is assumed that most adults carry this infection.

Once you have been infected, there is no cure for cold sores.

There are 2 different types of HSV that cause cold sores, HSV type 1 and HSV type 2; HSV type 1 is responsible for more than 90% of cold sores. 

HSV type 2 generally causes genital herpes, but if it infects skin around the mouth it can cause cold sores too.

HSV infections are mostly asymptomatic or unrecognised and can be spread, even if there are no cold sores/ blisters visible. 

Some infections will cause blisters and sores ranging from mild to more severe. 

Before cold sore lesions appear, they are often preceded by a sensation of pain, burning or numbness. Fluid filled blisters usually appear within 24 hours and weep until they scab over and heal. Episodes are usually mild and self limiting, settling on their own in 7-10 days.

If you have had a cold sore, it is quite likely you will have more. This is because the HSV that caused the initial episode lies dormant in the nerve cells in your skin (the nerve that supplies the area where the first lesions appeared) and has the potential to cause infection again, even after the blisters heal and disappear.

What can trigger a flare of cold sores?

Some people find that certain things/ situations trigger a cold sore to reappear including:

  • Feeling unwell eg with a viral infection or fever
  • Exposure to sunlight & wind 

(if you feel this is a trigger, apply a high factor moisturising sun cream every day)

  • Stress
  • Fatigue
  • Changes to the immune system
  • Injury to the skin

(try to avoid dry, chapped lips)

  • Hormonal changes eg at the start of your period

How do you stop a cold sore from spreading?

Cold sores are contagious from the moment of the first tingle until they have completely healed. There are some things you can do to reduce the risk of spread to others, or to other areas of your own body:

  • Try not to pick/ touch sores
  • Avoid kissing / skin contact with others
  • Avoid having oral sex (it could cause genital herpes)
  • Avoid sharing items that come into contact with the cold sore lesions: lip balm, towels, eating utensils and other personal items
  • Keep your hands clean: wash your hands carefully before you touch yourself or other people
  • Try to avoid triggers: the best way to avoid spreading cold sores is to avoid getting them.
  • If you get a warning sign, then act quickly: follow the advice above and consider treatment (creams or medication depending on your individual situation). 

Please be aware that you should be especially careful around those who are immunocompromised (weakened immune system) when you have active cold sore lesions, until they heal completely as HSV infection can be potentially very serious for these people.

Extreme caution is required around babies who are at risk of neonatal herpes,  a potentially life-threatening condition - do not kiss babies or young children if you have a cold sore. 

In some cases, antiviral medication is required to manage a flare of cold sores, e.g. frequent, severe episodes or if exposed to predictable triggers.

This medication should be taken as soon as possible after the symptoms start,or when you get warning signs (e.g. tingling). 

We can arrange a prescription for aciclovir (an antiviral medication) as a treatment for people who have previously been diagnosed with cold sores by a healthcare professional for:

  • A current outbreak
  • In preparation for the next recurrence 

This is subject to clinical suitability 

We are not able to offer prescriptions for other antiviral treatments via this service.

What is aciclovir?

Aciclovir is a medication used to treat HSV infection. 

It is not a cure for cold sores but it reduces the severity and duration of the outbreak by preventing the virus from multiplying. This also helps to reduce the spread of the virus. 

How do you take aciclovir?

  • You should take one tablet five times a day, for five days.
  • Space out the doses as evenly as possible during the day - you do not need to take this during sleeping hours. 
  • You can take aciclovir with or without food.
  • It may be useful to set an alarm on your phone, as it can be difficult to remember to take medication 5 times a day!
  • If you forget to take a dose, take it as soon as you remember and then continue as before. (Do not take two doses at the same time to make up for a missed dose). 
  • Complete this course of treatment, even if all your symptoms have resolved. 
  • Drink plenty of water to avoid dehydration and keep your kidneys working well. 
  • As your skin can become more sensitive to sunlight when taking this medication, avoid strong sun and sunbeds. Use a high protection sun factor.

What are the potential side effects of aciclovir?

  • nausea/ vomiting, diarrhoea or stomach aches
  • Headache
  • Rash
  • Photosensitivity (more sensitive to sunlight)
  • Dizziness
  • fatigue

If you are concerned about any of these symptoms, or you develop other symptoms which you feel may be related to this medication, please speak with your pharmacist or doctor for advice. 

When should I see a doctor?

There are some occasions when you should see a doctor face-to-face via a video consultation or your local GP:

  • If you are pregnant
  • If your lesions have been present for more than 10 days
  • If you are concerned that your lesions are getting worse despite treatment
  • If you develop lesions in a different location to where your lesions usually occur
  • If you have lesions inside your nose/ mouth/ ears, or areas other than you face

If you have lesions around your eye/ on your eye, please seek URGENT medical assessment 

  • If you have a weakened immune system 
  • If you are feeling generally unwell (e.g fever, headache, malaise)

These infections are potentially more complex to manage and require a more detailed assessment. 

Who Is This Service For?

This service is suitable if you :

  • Are 17 years of age or more 
  • Have been previously diagnosed with cold sores by a healthcare professional 
  • Require treatment for a current flare of cold sores or in preparation for future significant flare 
  • Your cold sore lesions are on your lips/ mouth/ chin area

This service is NOT suitable for you if:

  • You are requesting this treatment for another person (that is a person other than the named person on this account)
  • You are pregnant (or suspect you could be pregnant) or breastfeeding
  • This is the first time you have had a cold sore
  • You have new lesions that are not where your cold sore lesions usually occur
  • You require a prescription for a medication other than aciclovir tablets
  • You need a prescription for suppression therapy (a longer course of treatment to help prevent flares)
  • You are feeling unwell / have a temperature
  • You have severe kidney disease
  • You are immunocompromised (have a weakened immune system because of certain medical conditions, or medications you are taking)

Please book a video consultation or speak with your regular doctor as a more detailed clinical history is essential so appropriate treatment is provided; the required medication dose /duration is different to that available via this service.  

  • Your lesions are located in areas other than lips/ mouth/ chin area

If you have lesions on other areas of your face or inside your mouth, please book a video consultation or speak with your local GP.


If you have genital lesions, please use our genital herpes treatment service

How Does It Work?

  • Online consultations with Irish based doctors
  • Our doctors issue a prescription if medically safe and suitable
  • Valid in any Irish pharmacy to buy your medication
  • Prescription sent to your chosen pharmacy via secure email (Healthmail) within minutes of approval

The accuracy of the information you provide is very important for the safe prescribing of the most suitable type of medication. 

The information that you provide is treated with the same patient-doctor confidentiality as in a normal face-to-face consultation.