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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

FAQ's

How quickly does Aciclovir work for cold sores?
It works best when started at the very first signs of a cold sore — often reducing healing time by 1–2 days.

Can I take Aciclovir every day to prevent outbreaks?
Yes, in certain cases prescribers may recommend daily suppressive treatment for people with very frequent or severe outbreaks.

Is Aciclovir the same as Valaciclovir?
They work in the same way, but Valaciclovir is a newer version that is often taken less frequently.

Can children take Aciclovir?
Yes, but the dose will need to be adjusted. Always follow medical advice.

Will Aciclovir cure the herpes virus?
No — the virus remains in the body, but Aciclovir helps manage and control outbreaks.