Cold sores are very common. The World Health Organization estimates that around 64% of people under 50 worldwide carry herpes simplex virus type 1 (HSV-1), the virus behind most cold sores on the lips and face.1
For many people, outbreaks are rare. For others, they come back several times a year. Common triggers include sunshine, illness and periods.2
Antiviral cold sore treatment can help, but only if you use it properly. A few practical choices make a real difference to how well it works. Here are four ways to get the most from your cold sore treatment.
Tip 1: Start treatment at the first sign of tingling
The most important thing in cold sore treatment is timing. Antiviral creams such as aciclovir 5% cream work best when you start them at the very first stage of a cold sore. That's when you feel tingling, itching or burning, before any blister appears.3
At this stage, the virus has woken up and is starting to multiply. Applying cream now gives it the best chance of helping. In trials, the effect was modest: on average, treated cold sores healed a little sooner than untreated ones.3
You can still start the cream once blisters have formed. But the earlier you start, the better.3
Get cold sores often? Keep a tube of cream to hand, so you can start the moment you feel that familiar tingle.
Not sure it's a cold sore? Other things, like a mouth ulcer, a spot or impetigo, can look similar at first.2 A pharmacist can help you work out what it is.
Tip 2: Apply the cream correctly, and often enough
Aciclovir cold sore cream is usually applied five times a day, roughly every four hours, skipping the night.3 A practical routine could be 7am, 11am, 3pm, 7pm and 11pm. Phone reminders can help you stick to it.
Use a clean fingertip or cotton bud to dab a thin layer over the cold sore and the skin just around it. Dab it on rather than rubbing it in.2
Wash your hands before and after each application.3 That way, you're less likely to spread the virus to other parts of your face or to other people.
Do not rub the cream in or touch the sore more than you need to. Dab it on gently, then wash your hands.
How long you use it for depends on your cream, so always follow the leaflet for your exact product. Zovirax Cold Sore Cream, for example, is used for at least four days. If the sore hasn't healed, you can carry on for up to 10 days in total.3
Still there after 10 days? See a GP.2,3
“Start antiviral cream at the first tingle rather than waiting for a blister. With aciclovir cold sore cream, regular applications matter: use it five times a day, roughly every four hours while you're awake, following your pack's instructions. Dab it on gently and wash your hands before and afterwards.
Ana Carolina GoncalvesSuperintendent Pharmacist
Tip 3: Protect the area from the sun
Sunshine can trigger cold sores, so it's one of the best-known reasons they come back.2
If you have an active cold sore, try to keep the area out of direct sun where you can. Avoid putting other products directly on the sore while you're using treatment, unless a pharmacist says it's fine.
Prone to cold sores? Make SPF lip balm part of your holiday packing, and reapply it through sunny days.
The NHS recommends a sunblock lip balm (SPF 15 or above) when you're outside in the sun.2 It's a simple step that can help cut down how often the sun sets one off.
Tip 4: Avoid spreading the virus while you heal
Cold sores are contagious from the moment you first feel tingling until they've completely healed.2 They can easily spread to other people and to other parts of your body.
During an outbreak, do not kiss anyone, especially babies, and do not have oral sex until the cold sore has completely healed.2 Kissing a baby when you have a cold sore can cause neonatal herpes, which is very dangerous for newborns.2
It's also sensible not to share anything that touches your mouth, like cups, cutlery, lip balm or towels. Wash your hands with soap and water whenever you touch the sore.2
The virus can also affect your eyes. This can cause eye pain, a red eye or blurred vision, and it's important to get it treated, as it can sometimes affect your sight.4
Eye pain, a red eye that's getting worse or changes to your vision? Ask for an urgent GP appointment or contact NHS 111.
Finding outbreaks very large, painful or frequent? A GP may prescribe antiviral tablets.2 You can also speak to your pharmacist about your options.
Frequently asked questions
When should I start using cold sore treatment?
As soon as you notice the first signs of a cold sore. That's usually tingling, itching or burning on or around your lips, before any blister appears. Antiviral creams such as aciclovir work best when you start them at this early stage. You can still start once blisters have formed, but the earlier you begin, the better your chance of it helping.
How long does a cold sore last with treatment?
Most cold sores start to heal within 10 days, with or without treatment. Antiviral cream started early may shorten an outbreak a little, but it can't promise healing within a set number of days. See a GP if your cold sore hasn't started to heal within 10 days, or if it's very large or painful.
How often should I apply cold sore cream?
Aciclovir cold sore cream is usually applied five times a day, roughly every four hours, skipping the night. A routine like 7am, 11am, 3pm, 7pm and 11pm works for most people. How long you use it depends on your product, so follow the leaflet. Zovirax Cold Sore Cream, for example, is used for at least four days and up to 10.
Can I use cold sore cream on genital herpes?
No. Aciclovir cream sold for cold sores is only for the lips and face, and it must not be used to treat genital herpes. If you think you have genital herpes, speak to your GP or visit a sexual health clinic. If you've already been diagnosed, Pharmica's prescribers can assess whether treatment is suitable for you through an online consultation.
Does cold sore cream still work once a blister has appeared?
Yes, you can still use it once a blister has appeared. But antiviral cream is best started at the earliest tingling stage, before anything is visible. So if you get cold sores often, keep a tube to hand. Then you can start straight away next time, and give the cream its best chance of helping.
References
- World Health Organization. Herpes simplex virus. World Health Organization; 2025. who.int
- NHS. Cold sores. NHS website; 2024. nhs.uk
- Haleon UK Trading Limited. Zovirax Cold Sore Cream: Summary of Product Characteristics. Electronic Medicines Compendium; 2023. medicines.org.uk/emc
- NHS. Herpes simplex eye infections. NHS website; 2026. nhs.uk
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.