Getting regular cold sore outbreaks or looking to prevent one in the run up to a big event? There are treatments available to prevent cold sores and to treat recurrent breakouts.
What are cold sores?
Cold sores are small blisters filled with fluid (1). They can appear anywhere on the face (1) but usually appear on or around the lips of your mouth (2).
What are the symptoms of cold sores?
Before a cold sore forms, most people feel an itchy, tingling, or burning feeling (1) around their lips (2). After about a day, a cold sore, or multiple cold sores, appear (2). Cold sores can feel painful.
Sometimes, cold sores can burst (1). This can be caused by talking, eating, or laughing (2). When they burst, fluid usually comes out (2). They then become crusty, forming scabs (1).
What are cold sores caused by?
Cold sores are caused by a virus called herpes simplex virus (HSV) (2).
There are two types of HSV:
- HSV Type 1 (HSV-1) can cause cold sores and genital herpes (3)
- HSV Type 2 (HSV-2) can also cause genital herpes (3)
Most people are infected by HSV when they’re children, after close skin-to-skin contact (1). For example, a family member with a cold sore may kiss a child on or near the lips, passing on the virus (1).
Once you’ve been exposed to the virus, you have it in your body for life. Most of the time, there are no symptoms but sometimes HSV causes a cold sore to form.
Certain things can trigger a cold sore (1), such as:
- Feeling tired for a long period of time
- Being ill
- Being on your period if female
- Light from the sun
Are cold sores contagious?
Yes, cold sores and the virus that causes them, HSV, are contagious (1). This means they can be passed on to other people (1). To stop passing on your cold sores and HSV make sure you avoid:
- Touching your cold sores (only touch them if you’re applying a cream to treat them and make sure you wash your hands with soap and water thoroughly after)
- Kissing anyone until your cold sores are completely healed
- Having oral sex as this can cause genital herpes
Are cold sores spots?
No, cold sores are not spots (1). They are contagious blisters caused by a virus, HSV (2).
Sometimes, they are confused with:
- Spots or boils that are red, filled with pus, and are sometimes painful
- Mouth ulcers that form on the inside of your lip or mouth
- Impetigo, a contagious skin condition where red blisters burst quickly and form golden-brown patches
Are cold sores a sexually transmitted infection (STI)?
An STI is usually passed on through unprotected sexual contact including vaginal, anal, and oral sex (4).
Generally, cold sores are not considered to be an STI. However, HSV (the virus that causes cold sores) can be passed onto someone else if your cold sore comes into contact with their genitals (such as a penis, testicle, vulva, or vagina). If HSV is spread to the genitals, this can cause genital herpes, an STI (4).
Using condoms can help protect against STIs. However, they can’t fully protect against all STIs, including genital herpes (3). This is why you should avoid oral sex completely until your cold sore is gone (1).
Without treatment, STIs can be serious (5). Not all STIs have symptoms so if you’re sexually active, you should get tested for STIs regularly (6). If you think you have an STI, you should speak to your doctor and get treatment as soon as possible (6).
How are cold sores diagnosed?
Cold sores are generally a clinical diagnosis (2). This means they are diagnosed based on the symptoms and by looking at the area of skin that is affected. If you experience tingling or itching on or around your lips, this is a sign that you’re going to get a cold sore (2). Talk to a pharmacist or your GP if you are worried about a cold sore or your symptoms (1).
How are mild cold sores treated?
Cold sores generally clear up on their own in around 10 days (1). However, if they are particularly painful or won’t go away, you may be able to use treatment (1).
You can:
- Take painkillers such as paracetamol or ibuprofen to help with the pain
- Drink water regularly to stay hydrated, so your body can fight the infection and heal your cold sores
- Wear sunscreen with a high SPF when you are outside to stop sunlight making your cold sores flare up
- Apply a cold sore cream that contains Aciclovir (also known as acyclovir), such as Zovirax (7) or a generic version (8), to help clear your cold sores (7)
How do cold sore creams work?
Cold sore creams usually contain Aciclovir. Aciclovir is an antiviral ingredient, which means it fights against viruses, such as HSV, to stop them from growing and spreading. This makes it easier for the body to heal cold sores (8).
Ideally, you should apply a cold sore cream as soon as you feel a tingling, burning, or itching sensation on or around your lips (8). You should then apply it to any cold sores that form. Apply a thin layer of Aciclovir cream 5 times a day, every 4 hours. For example, apply the cream at 7 am, 11 am, 3 pm, 7 pm, and 11 pm (7).
How are more severe cold sores treated?
For people who have multiple cold sores, keep getting cold sores, or get cold sores that are large or painful, prescription treatment may be needed.
If appropriate, a doctor may prescribe 200mg Aciclovir (10) or 500mg Valaciclovir (11) tablets to help speed up the healing process. These tablets are stronger than cold sore creams and are only available on prescription (9).
Is there a treatment to prevent getting a cold sore?
Yes, some prescription treatments, like 400mg Aciclovir (12) or 500mg Valaciclovir (13) tablets can be used to prevent cold sores (9).
We may consider prevention treatment if you:
- Keep getting cold sores or they are very painful
- Don’t want to risk getting one for an event, like a wedding
- Have a history of cold sores being triggered at a certain time, like a sunny holiday or change of season
What are the different prescription cold sore treatments?
Our clinical team will consider different prescription treatments, depending on whether you need to prevent cold sores or treat existing ones (9).
Depending on whether treatment is for prevention or active outbreak, the tablets may have different amounts of medicine in them (different strengths, usually in mg). These tablets area also taken a different number of times per day (9).
To treat cold sores, treatment options we consider are:
- 200mg Aciclovir tablets (10)
One 200mg tablet, 5 times per day. This is taken for 5 days and can continue up to 10 days if new cold sores appear during treatment. (10) - 500mg Valaciclovir tablets (11)
One 500mg tablet, 2 times per day. This is taken for 5 days. (11)
To prevent cold sores, treatment options we consider are:
- 400mg Aciclovir tablets (12)
One 400mg tablet, 2 times per day. (12) - 500mg Valaciclovir tablets (13)
One 500mg tablet per day. (13)
We may also discuss with you a multipack of 400mg Aciclovir tablets (14). This is useful if a pharmacist or doctor has recommended that you take long-term prevention treatment for cold sores (9). This is usually for people who keep getting cold sores, especially if they are large, painful, or multiple appear at once (9).
Am I eligible for treatment that prevents a cold sore?
If you have a history of cold sores and are otherwise well, the online doctor may consider prescribing treatment. This is assessed through our online consultation.
What are the side effects of cold sore treatment?
Some common side effects of Aciclovir (15) and Valaciclovir (16) include :
- Headache (15, 16)
- Feeling dizzy or like you’re going to be sick (nausea) (15, 16)
- Being sick (vomiting) (15, 16)
- More often, loose, or runny poos (diarrhoea) (15, 16)
- Skin becomes more sensitive to UV rays and light, causing a rash, redness or itching (photosensitivity reaction) (15, 16)
These may affect more than 1 in every 10 people who use this medicine. You can speak to a pharmacist or doctor about the side effects of treatment. Always report any side effects that concern you to a healthcare professional.
Where can I get cold sore treatment?
You need a prescription from a pharmacist or doctor to get Aciclovir or Valaciclovir.
You can request treatment directly using our website:
- Select your medical condition or a preferred treatment
- Click ‘Start my online consultation’
- Complete the consultation form
Your consultation will be reviewed by an independent UK-registered doctor, who will determine whether a prescription is appropriate. If approved, your treatment will be dispensed by our pharmacy team.
Should I use generic or branded cold sore treatment?
Generic and branded treatments usually contain the same active ingredient and work in the same way (9). For example, generic Valaciclovir tablets and Valtrex (branded) (17) both contain Valaciclovir, which stops the growth of HSV (13).
Sometimes the other ingredients in branded and generic treatments may differ slightly (9).
Some people prefer branded treatments but generic treatments are usually much cheaper (16) and the only key difference is usually the packaging (18). It’s completely up to you which you want to use (16). We offer both generic and branded treatments (18).
You can find out more about the difference between generic and branded treatments in this article: Generic and branded medicines - why you should know the difference (9).
Where can I find out more?
- Cold sores [Internet]. NHS. 2024 Feb 19.
- Overview: Cold sores [Internet]. Institute for Quality and Efficiency in Health Care (IQWiG). 2025 Jan 14.
- About Genital Herpes [Internet]. Genital Herpes. Centers for Disease Control and Prevention (CDC). 2024 Feb 20.
- Genital herpes [Internet]. NHS. 2023 Jun 27.
- The dangers of undiagnosed sexually transmitted infections [Internet]. American Society for Microbiology. 2022 Dec 8.
- Sexually transmitted infections (STIs) [Internet]. NHS. 2024 May 13.
- Zovirax cold sore cream 2g tube [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Aciclovir 5% cream 2g [Internet]. Oxford Online Pharmacy. 2021 Jun 10.
- Cold Sore Treatments & Remedies [Internet]. Oxford Online Pharmacy. 2024 Jul 30.
- Aciclovir 200mg 50 tablets (outbreak) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Valaciclovir 500mg 20 tablets (outbreak) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Aciclovir 400mg 56 tablets (prevention) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Valaciclovir 500mg 84 tablets (Prevention) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Aciclovir 400mg 168 tablets (prevention) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Side effects of Aciclovir [Internet]. NHS. 2022 Jul 01.
- Valaciclovir [Internet]. NICE (National Institute for Health and Care Excellence) BNF (British National Formulary). 2025.
- Valtrex 500mg 20 tablet (outbreak) [Internet]. Oxford Online Pharmacy. 2023 Mar 20.
- Generic and branded medicines - why you should know the difference [Internet]. Oxford Online Pharmacy. 2022 Mar 14.