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Aciclovir - Cold Sore Treatment

Aciclovir - Cold Sore Treatment

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  • ✔️ Targets herpes simplex virus directly to shorten cold sore duration
  • ✔️ Works best when applied at first tingle or itch
  • ✔️ Clinically established antiviral active ingredient: aciclovir 5%
  • ✔️ Suitable for adults and adolescents aged 12 and over
  • ✔️ Convenient topical cream — no prescription required

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What Is Aciclovir Cold Sore Cream?

 

Cold sores are one of those things that always seem to appear at the worst possible moment — before a big event, when you're run down, or right after a bout of illness. They're caused by the herpes simplex virus type 1 (HSV-1), a virus that lies dormant in nerve tissue and reactivates when your immune system is under pressure. Aciclovir cold sore cream is a clinically established antiviral treatment that targets this virus directly, helping to reduce the severity and duration of an outbreak. You can browse our full range of creams and ointments if you're looking for other topical treatments alongside this one.

Aciclovir 5% cream is available over the counter in the UK without a prescription. It's one of the most widely recommended first-line treatments for cold sores by pharmacists and GPs alike, and it's been used safely for decades. Each tube contains aciclovir as the active ingredient at a concentration of 5%, formulated for direct application to the affected skin.

 

How Does Aciclovir Cold Sore Cream Work?

 

Aciclovir is a synthetic nucleoside analogue — which essentially means it mimics one of the building blocks that the herpes simplex virus needs to copy its own DNA. Once applied to the skin, it's taken up by virus-infected cells and converted into its active form by a viral enzyme called thymidine kinase. From there, it interferes with the virus's ability to replicate.

  • Aciclovir is absorbed into cells infected with HSV-1
  • Viral thymidine kinase converts it into aciclovir monophosphate
  • Cellular enzymes further convert it to aciclovir triphosphate
  • Aciclovir triphosphate blocks viral DNA polymerase, halting replication
  • Healthy, uninfected cells are largely unaffected, reducing side effects

Because the activation process depends on a viral enzyme, aciclovir is selectively toxic to infected cells. This targeted mechanism is why it's well tolerated when used topically.

 

Who Should Use Aciclovir Cold Sore Cream?

 

This cream is suitable for adults and children aged 12 and over who experience recurrent cold sores on the lips or face caused by HSV-1. It's particularly useful for people who recognise their early warning signs — that familiar tingling or itching — and want to act quickly before a blister develops.

  • Adults and adolescents aged 12 and over
  • People with a confirmed history of cold sore outbreaks
  • Those who want an OTC antiviral option without a GP visit
  • Individuals who prefer topical treatment over oral antivirals

 

How Does Aciclovir Cream Compare to Other Cold Sore Treatments?

 

Feature Aciclovir 5% Cream Penciclovir 1% Cream
Active ingredient Aciclovir Penciclovir
Application frequency 5 times daily for 5 days Every 2 hours for 4 days
Available OTC in UK Yes Yes
Suitable for children (12+) Yes Check product labelling

 

Is Aciclovir Cold Sore Cream Safe to Store at Home?

 

Yes — aciclovir cold sore cream is straightforward to store. Keep it below 25°C, away from direct sunlight and out of reach of children. Do not freeze the cream, as this can affect the formulation. Once opened, check the expiry date on the tube and do not use it beyond that date. If you're managing other skin conditions at the same time, our skin care collection has a range of complementary products that may help.

This product is a medicine. Speak to your doctor or pharmacist before using if you have an underlying medical condition or are taking other medicines.

Aciclovir Cold Sore Treatment specifications
Treatment category Antiviral / Cold Sore Treatment
Active ingredient Aciclovir 5%
Mechanism of action Inhibits herpes simplex virus DNA polymerase
Effective against Herpes simplex virus type 1 (HSV-1)
Suitable for Adults and children aged 12 and over
Strengths 5% w/w
Preparation Cream
Route of administration Topical (external use only)
UK classification Pharmacy (P) medicine
Drug class Nucleoside analogue antiviral
Pack sizes 2g

Specifications of Aciclovir Cold Sore Treatment

 

What Is Aciclovir Cream and What Is It Used For?

 

Aciclovir 5% cream is a topical antiviral medicine used to treat cold sores on the lips and face. Cold sores are caused by the herpes simplex virus type 1 (HSV-1), which remains dormant in the body and can reactivate during periods of stress, illness, sun exposure, or hormonal change. The cream does not cure the virus — it cannot remove it from your body — but it does reduce how long a cold sore lasts and can lessen its severity, particularly when treatment begins early. According to the NHS, cold sores usually clear up on their own within 7 to 10 days, but antiviral creams like aciclovir can speed up this process.

 

What Do You Need to Know Before Using Aciclovir Cream?

 

Before applying this cream, there are some important things to consider. Not everyone is suitable for this treatment, and certain conditions or medicines may affect whether it's right for you.

Do not use this cream if you:

  • Are allergic to aciclovir, valaciclovir, propylene glycol, or any other ingredient in the formulation
  • Have a cold sore inside your mouth or on your genitals — this cream is for external facial use only
  • Are under 12 years of age
  • Have a severely weakened immune system (e.g. due to HIV or chemotherapy) — seek GP advice first

Speak to your pharmacist or GP before use if you:

  • Are pregnant or breastfeeding
  • Have eczema or broken, inflamed skin near the affected area
  • Are using any other topical medicines on the same area

Drug interactions:

  • Topical aciclovir has no clinically significant interactions with other medicines when used as directed on the skin
  • If you are taking oral antiviral medicines, speak to your pharmacist before combining treatments

 

How Should You Use Aciclovir Cream?

 

Timing is everything with cold sore treatment. The sooner you apply the cream after noticing that first tingle or itch, the better the outcome. Here's how to use it correctly:

  1. Wash your hands thoroughly with soap and water before and after each application
  2. Using a clean fingertip or cotton bud, apply a thin layer of cream to the cold sore and the skin immediately surrounding it
  3. Gently smooth the cream over the area — do not rub vigorously
  4. Apply five times a day, approximately every four hours (you can skip the night-time dose if needed)
  5. Continue for a full five days, even if the cold sore appears to be healing
  6. Avoid touching your eyes or mouth after application
  7. Do not share the tube with anyone else
Indication Age Group Dose Frequency
Cold sore (HSV-1) Adults and children 12+ Small amount applied topically 5 times daily for 5 days
Cold sore (HSV-1) — immunocompromised Adults (GP supervision) As directed by GP Up to 5 times daily for up to 10 days

If your cold sore has not improved after five days of treatment, or if it gets significantly worse, stop using the cream and speak to your GP or pharmacist. You may also find it helpful to explore our skin care range for products that support skin recovery after a cold sore heals.

 

What Are the Possible Side Effects of Aciclovir Cream?

 

Like all medicines, aciclovir cream can cause side effects, although not everyone experiences them. Most side effects are mild and localised to the area where the cream is applied.

Common side effects (may affect up to 1 in 10 people):

  • Mild burning or stinging sensation at the application site
  • Itching around the treated area
  • Temporary skin dryness or flaking

Less common side effects (may affect up to 1 in 100 people):

  • Redness or mild skin irritation
  • Contact dermatitis (skin reaction to an ingredient in the cream)
  • Swelling of the lips or face — stop use immediately and seek medical advice if this occurs

Serious allergic reactions (anaphylaxis) are very rare but require immediate medical attention. Signs include difficulty breathing, severe swelling, or a widespread rash. If you experience any of these, call 999 or go to your nearest A&E.

 

How Should You Store Aciclovir Cream?

 

Correct storage keeps the cream effective for its full shelf life. Follow these simple guidelines:

  • Store below 25°C in a cool, dry place
  • Do not freeze
  • Keep away from direct sunlight and heat sources
  • Keep the tube tightly closed when not in use
  • Store out of sight and reach of children
  • Do not use after the expiry date printed on the tube
  • Do not dispose of medicines via household waste — return unused cream to your pharmacy

If you're looking for other health essentials to keep at home, our first aid collection has a wide range of products for everyday health needs.

Written and reviewed by our qualified team

Your safety and success are our highest priorities. Our medical team rigorously evaluates every product and piece of advice we provide, ensuring you receive only the most effective, science-backed solutions available.

Frequently Asked Questions

Where can I buy aciclovir cold sore cream online in the UK?

You can buy aciclovir cold sore cream directly from Cured Pharmacy, a GPhC-registered UK online pharmacy, for £19.99. No prescription is needed — it's available as an over-the-counter pharmacy medicine. Simply add it to your basket and complete a brief health check at checkout to confirm it's suitable for you.

How does aciclovir cold sore cream work in the body?

Aciclovir is a nucleoside analogue antiviral that mimics one of the building blocks the herpes simplex virus needs to copy its DNA. Once absorbed into virus-infected skin cells, it's activated by a viral enzyme and then blocks the virus's DNA polymerase, stopping it from replicating. Healthy, uninfected cells are largely unaffected, which is why the cream is well tolerated.

How do I apply aciclovir cold sore cream step by step?

Wash your hands before and after each application. Apply a small amount of cream to the cold sore and the surrounding skin using a clean fingertip or cotton bud, five times a day for five days. Avoid getting the cream in your eyes or mouth, and do not share the tube with anyone else.

When is the best time to start using aciclovir cold sore cream?

Start applying the cream at the very first sign of a cold sore — that familiar tingling, itching, or burning sensation — ideally before a blister has formed. Early treatment gives the antiviral the best chance of limiting the outbreak. Waiting until the blister is fully developed reduces how effective the cream can be.

What are the side effects of aciclovir cold sore cream?

Most side effects are mild and localised to the skin where the cream is applied, including stinging, itching, or temporary dryness. Less commonly, some people experience redness or a mild skin reaction. Serious allergic reactions are rare — if you notice swelling, difficulty breathing, or a widespread rash, stop use immediately and seek urgent medical help.

Who is eligible to use aciclovir cold sore cream?

This cream is suitable for adults and children aged 12 and over who have cold sores on the lips or face caused by HSV-1. It is not suitable for use inside the mouth, on genital herpes, or in children under 12. People with severely weakened immune systems should speak to their GP before using it.

Can I use aciclovir cold sore cream during pregnancy?

Topical aciclovir is considered low risk during pregnancy because very little of the active ingredient is absorbed through the skin into the bloodstream. However, the NHS recommends speaking to your GP or pharmacist before using any medicine while pregnant or breastfeeding. It's always better to get personalised advice rather than self-treating without guidance.

How long does aciclovir cold sore cream take to work?

When applied at the first sign of a cold sore, aciclovir cream can reduce healing time by approximately one day compared to no treatment. Most cold sores resolve within seven to ten days regardless, but the cream can reduce severity and discomfort during that time. Consistent application five times daily throughout the five-day course is essential for the best outcome.

What happens if I miss a dose of aciclovir cold sore cream?

If you forget to apply the cream at one of your scheduled times, apply it as soon as you remember and then continue with your regular schedule. Do not apply a double amount to make up for a missed application. Missing the odd dose is unlikely to significantly affect the outcome, but try to keep to the five-times-daily routine as closely as possible.

What are the alternatives to aciclovir cold sore cream?

The main alternative topical antiviral available OTC in the UK is penciclovir 1% cream (Vectavir), which is applied every two hours for four days. Oral antivirals such as valaciclovir or aciclovir tablets are available on prescription for more frequent or severe outbreaks. You can also explore our skin care range for supportive products that help soothe irritated skin during an outbreak.

How long can you use aciclovir cold sore cream for?

Each course of treatment lasts five days, applied five times daily. If your cold sore has not improved after five days, do not continue using the cream without speaking to a pharmacist or GP first. For people who get frequent recurrent cold sores, a GP may consider prescribing oral antiviral suppressive therapy rather than repeated topical courses.

Can aciclovir cold sore cream be used on children?

Aciclovir 5% cream can be used in children aged 12 and over at the same dose as adults. It is not licensed for use in children under 12, and you should seek GP advice if a younger child develops a cold sore. Always keep the tube out of reach of children and supervise application in younger teenagers.

Does aciclovir cold sore cream interact with other medicines?

When used topically as directed, aciclovir cream has no clinically significant interactions with other medicines because very little is absorbed into the bloodstream. If you are already taking oral antiviral medicines, speak to your pharmacist before using the cream as well. Always mention all medicines you are taking — including over-the-counter products — when speaking to a healthcare professional.

What are the latest studies on aciclovir for cold sores?

Aciclovir has been studied extensively since the 1980s and remains a well-evidenced first-line topical antiviral for HSV-1 cold sores. Published clinical literature consistently supports its use when applied early in the outbreak cycle. The NHS and BNF continue to recommend it as a standard OTC option for recurrent cold sores in adults and adolescents.

How do I manage side effects of aciclovir cold sore cream?

Mild stinging or dryness at the application site usually settles on its own and does not require you to stop treatment. If skin irritation is bothersome, try applying the cream with a cotton bud rather than your fingertip to minimise friction. If you develop a more significant skin reaction or any signs of allergy, stop using the cream and speak to your pharmacist — you can also browse our skin care collection for gentle soothing products.

How Should You Use Aciclovir Cold Sore Cream?

Using aciclovir cream correctly makes a real difference to how quickly your cold sore heals. Always apply it as soon as you notice the first signs of an outbreak — that tingling or itching sensation is your cue to act. Follow these steps each time you apply the cream:

If you accidentally get the cream in your eyes, rinse thoroughly with clean water and seek medical advice if irritation persists.

What Is the Correct Dose of Aciclovir Cold Sore Cream?

The dose is the same for all eligible users — a small amount applied directly to the cold sore five times a day. There is no need to apply a thick layer; a thin, even coating over the affected area is all that's required. Do not apply more frequently than directed, as this will not speed up healing and may increase the risk of skin irritation.

When Is the Best Time to Use Aciclovir Cold Sore Cream?

Timing your applications evenly throughout the day gives the cream the best chance of working. Space your five daily applications roughly four hours apart — for example, at 7am, 11am, 3pm, 7pm, and 11pm. You can skip the overnight application if needed, but try to keep the daytime doses as evenly spaced as possible. Starting treatment at the very first sign of a cold sore — before a blister has fully formed — is when aciclovir is most effective.

How Long Can You Use Aciclovir Cold Sore Cream For?

Each treatment course lasts five days. Do not stop early just because the cold sore looks like it's improving — completing the full course helps ensure the virus is properly suppressed. If the cold sore has not healed after five days, do not continue applying the cream without speaking to a pharmacist or GP first. For people who experience very frequent outbreaks, a GP may recommend oral antiviral suppressive therapy as a longer-term option.

Do not exceed the recommended dose. If in doubt, speak to your pharmacist.

What Are the Most Common Side Effects of Aciclovir Cold Sore Cream?

Most people who use aciclovir cream tolerate it well, and side effects — when they do occur — are usually mild and confined to the area where the cream is applied. They tend to settle on their own without needing to stop treatment.

  • Mild burning or stinging sensation immediately after application
  • Itching around the treated area
  • Temporary skin dryness or flaking at the application site

These reactions are generally short-lived. If the stinging is uncomfortable, try applying the cream with a cotton bud rather than your fingertip to reduce friction on already-sensitive skin.

What Are the Less Common Side Effects of Aciclovir Cold Sore Cream?

A smaller number of people may experience slightly more noticeable skin reactions. These are still generally mild but worth being aware of before you start treatment.

  • Redness or mild inflammation at the application site
  • Contact dermatitis — a skin reaction that may be caused by propylene glycol, one of the inactive ingredients in the cream
  • Peeling or crusting of the skin around the treated area
  • A feeling of tightness in the skin after the cream dries

If you develop contact dermatitis or notice that your skin is reacting more than expected, stop using the cream and speak to your pharmacist. They can advise on whether an alternative treatment would be more suitable for you.

What Are the Serious Side Effects of Aciclovir Cold Sore Cream?

Serious side effects from topical aciclovir are very rare, largely because very little of the active ingredient is absorbed into the bloodstream through intact skin. However, allergic reactions can occasionally occur and require prompt attention.

Signs of a serious allergic reaction (anaphylaxis) include sudden swelling of the face, lips, or throat, difficulty breathing, a widespread skin rash, or dizziness. If you experience any of these symptoms after applying the cream, stop use immediately, call 999, or go to your nearest A&E department. Do not wait to see if symptoms improve on their own.

What Should You Do If You Experience Side Effects?

For mild side effects such as stinging or dryness, you can usually continue treatment and the symptoms will settle. Applying the cream with a cotton bud, keeping the area clean, and avoiding other skincare products on the same spot can all help reduce irritation. If side effects are persistent, worsening, or causing significant discomfort, stop using the cream and seek advice from your pharmacist or GP. You can also report side effects directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Can Aciclovir Cold Sore Cream Interact With Other Medicines?

When used topically as directed, aciclovir cream has no clinically significant interactions with other medicines. Because absorption through the skin is minimal, the risk of systemic drug interactions is very low. That said, if you are already taking oral antiviral medicines — such as aciclovir tablets or valaciclovir — speak to your pharmacist before using the cream at the same time. Always tell your pharmacist or GP about all medicines you are currently taking, including over-the-counter products and supplements.

If you are concerned about any side effects, contact your pharmacist or GP immediately.

Patient Information Leaflet

Important - Before taking any medication, it is always important to read the Patient Information Leaflet (PIL)

Written and reviewed by our qualified team

GPhC Number: 2233073
Tarun Kumar

Reviewed by:

Tarun Kumar

Superintendent/ Clinical Lead

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Content last updated: 31 Mar 2025

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