• Speeds up healing and shortens outbreaks
  • Reduces pain, redness, and swelling
  • Helps prevent cold sores returning in frequent sufferers

How it works?

Online Consultation

We ask you to complete a quick and easy consultation and get you started.

Choose condition

We have a selection of treatments available for various conditions.

Express Delivery

You will have complete visibility and control of your delivery.
Notice!

Before ordering this treatment, you may have to complete an online consultation

Overview

Struggling with painful or recurrent cold sores? Aciclovir Tablets work from the inside out to stop the herpes virus multiplying, helping outbreaks heal faster and reducing the risk of them coming back.

For many people, this prescription antiviral is a game-changer — cutting down the discomfort, shortening healing time, and making flare-ups far more manageable. Taken at the first sign of a tingle, Aciclovir can help you stay one step ahead of cold sores.

This medicine requires a secure online consultation with a UK-registered prescriber, and will only be supplied if clinically appropriate.


What is Aciclovir 


Aciclovir is an antiviral medicine used to treat infections caused by the herpes simplex virus (HSV-1) — the virus responsible for cold sores. It works by stopping the virus from multiplying, which helps your body control the infection more effectively.

Although aciclovir does not remove the virus from the body, taking it during an outbreak can shorten the duration of cold sores, speed up healing, and reduce pain, swelling, and redness. It also helps to lower the risk of spreading the virus to others.

For people who experience frequent outbreaks, aciclovir can also be used as a preventive treatment to reduce how often cold sores return, giving greater control and confidence in day-to-day life.

Directions

  • Take exactly as prescribed by your clinician.
  • The typical dose for cold sores is 200mg, five times daily (every 4 hours while awake) for 5 days.
  • Swallow the tablets whole with water, with or without food.
  • Start treatment as soon as symptoms appear (e.g. tingling, burning).
  • If you miss a dose, take it as soon as you remember — unless it’s nearly time for the next one.

Side Effects

Most people tolerate Aciclovir well, but like all medicines, it can cause side effects in some individuals. These are usually mild and temporary.

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

  • Headache – often mild and manageable.
  • Nausea or vomiting – taking Aciclovir with food may help.
  • Diarrhoea – usually settles without treatment.
  • Dizziness – avoid driving or using machinery if affected.


Rare but serious (seek medical advice):

  • Skin rash or itching
  • Shortness of breath or facial swelling
  • Unexplained bruising or bleeding
  • Confusion or hallucinations – more likely in older adults or those with kidney problems


Disclaimer: This is not a complete list of side effects. Always read the patient information leaflet that comes with your medicine for full details. If you notice anything unusual or concerning, stop using the medicine and seek medical advice promptly. In an emergency, call 999 or go to A&E.

Warnings

Do not take Aciclovir if you:

  • Are allergic to aciclovir, valaciclovir, or any ingredients in the tablets
  • Have kidney problems, unless your doctor has adjusted your dose
  • Are pregnant or breastfeeding, unless specifically advised by your clinician


Other cautions:

  • Stay well hydrated while taking Aciclovir
  • Tell your prescriber about any other medicines you take (especially for kidney problems or immune conditions)
  • Long-term or preventative use should only be under specialist supervision
Frequently asked questions

  • What are aciclovir tablets used for in cold sores?

    Aciclovir tablets help treat cold sore outbreaks by stopping the virus from multiplying, which can shorten healing time and reduce symptom severity. They are often used when outbreaks are frequent or more severe than usual.

  • How do aciclovir tablets work to treat cold sores?

    Aciclovir slows down how the herpes simplex virus replicates, helping your immune system bring the outbreak under control more quickly. This can reduce pain, swelling and the duration of the blister stage.

  • How should I take aciclovir tablets for a cold sore outbreak?

    Aciclovir tablets are usually taken three times a day for 5 days, ideally as soon as tingling or burning begins. Taking them early gives the best chance of reducing the severity and speed of the outbreak. Follow the dose recommended by your clinician.

  • How quickly do aciclovir tablets start working?

    Aciclovir tablets begin working soon after the first dose, although you may not feel improvement for one to two days.Starting treatment at the earliest sign of a cold sore usually provides the best results.

  • Are aciclovir tablets effective for severe or recurrent cold sores?

    Yes. Aciclovir tablets are often used when cold sores are frequent, large or slow to heal. They can shorten recovery time and may be used preventatively in people with regular outbreaks. A clinician will help decide if this is suitable for you.

  • Who should avoid aciclovir tablets?

    People with kidney problems, weakened immune systems or allergies to antiviral medicines may need alternative treatments. Always tell your clinician about your medical history, pregnancy status and any medicines you take before starting aciclovir.

  • What are the common side effects of aciclovir tablets?

    Side effects can include nausea, stomach upset, headache or tiredness. These are usually mild and short-lived. Rarely, dizziness or kidney-related issues occur, especially if you are dehydrated. Drink plenty of water during treatment.

  • Can aciclovir tablets stop a cold sore from fully developing?

    Sometimes. If taken at the first sign of tingling or burning, aciclovir tablets may prevent a blister from forming or reduce how severe it becomes. Early treatment helps slow the virus before it spreads across the skin.

  • Do aciclovir tablets help with cold sores triggered by stress or illness?

    Yes. Stress, tiredness and illness can weaken immunity, making outbreaks more likely.Aciclovir tablets work the same regardless of the trigger by slowing viral activity and helping shorten the episode.

  • Can I take aciclovir tablets alongside topical cold sore creams?

    Yes. Many people use aciclovir tablets with antiviral creams to ease symptoms locally while the tablets work internally. Your clinician can advise on the best combination based on your outbreak pattern.

  • Are aciclovir tablets suitable for frequent outbreaks?

    They can be. Some people take short courses for each outbreak, while others use low-dose aciclovir daily to reduce how often cold sores appear. Your clinician will discuss whether suppressive treatment is appropriate.

  • Can I drink alcohol while taking aciclovir tablets?

    Moderate alcohol is generally safe, but large amounts may worsen dehydration, which increases the risk of aciclovir-related kidney side effects. Drink water regularly if you choose to drink alcohol during treatment.

  • Are aciclovir tablets safe in pregnancy or breastfeeding?

    Aciclovir is sometimes used in pregnancy, but you should always check with a clinician first. They will confirm whether tablets are necessary and safe based on your symptoms and health history.

  • What should I do if I miss a dose of aciclovir tablets?

    Take it as soon as you remember unless it is nearly time for the next dose. Do not double up to make up for a missed tablet. Keeping doses evenly spaced helps maintain antiviral effect.

  • Can aciclovir tablets prevent cold sores before major events?

    Yes. Some people take aciclovir tablets preventatively when they anticipate triggers, such as stress, sun exposure or important events. Your clinician can advise if this approach is suitable for you.

Related Treatments for Cold Sores