Cold sores are very common. The World Health Organization estimates that around 67% of people under 50 worldwide carry herpes simplex virus type 1 (HSV-1), the virus behind cold sores on the lips and face.1
For many people, outbreaks are rare. For others, they can happen several times a year, triggered by sunlight, stress, illness or hormonal changes.2
Antiviral cold sore treatment can make an outbreak shorter and less severe, but only if you use it properly. The difference between a cold sore that clears quickly and one that drags on often comes down to a few practical choices. 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 during the very first stage of a cold sore. That's the short window, usually a few hours to a day or two, when you feel tingling, itching or burning before any blister appears.
At this stage, the virus has woken up in your nerve cells and is starting to multiply. Applying antiviral cream now can interrupt that process and make the outbreak less severe.3
Not sure it's a cold sore? Ask a pharmacist, as other skin infections can look similar early on.
Once blisters have fully formed, treatment can still help ease your symptoms, but you've missed the window when it works best. Starting within the first 24 hours gives you the best chance of a quicker recovery.
If you get cold sores regularly, keeping a tube of cream handy means you can act as soon as you notice that familiar warning feeling. That alone makes a bigger difference than almost anything else you can do.
Tip 2: Apply the cream correctly, and often enough
Apply aciclovir cold sore cream five times a day, roughly every four hours.4 For most people, a practical routine could look like this: 7am, 11am, 3pm, 7pm and 11pm.
Sticking to that is important, because antiviral creams need steady contact with the affected skin to keep working. Missed doses can make them less effective.
Use a clean fingertip or cotton bud to dab a thin layer over the cold sore and the skin just around it. Don't rub it in hard, as gently dabbing lowers the risk of spreading the virus to the skin around it.5
Do not share your tube of cream with anyone else, even family. It can pass the virus on.
Wash your hands thoroughly before and after each application, so you don't pass the virus to other parts of your face or to other people.
The standard course is five days. If the cold sore hasn't healed after five days, you can carry on for another five days. If it still hasn't cleared after ten days in total, stop using the cream and speak to your doctor or pharmacist.
Tip 3: Protect the area from the sun
Ultraviolet (UV) light is one of the best-known triggers for cold sores coming back. Sun exposure can wake the virus up in your nerve cells and bring on a new outbreak. That's why cold sores often flare up in summer, or after a sunny holiday.6
So there are two things to keep in mind. If you have an active cold sore, try to keep the area out of direct sun as much as possible. Avoid putting other products, like lip balm, directly on the cold sore while you're using treatment, unless a pharmacist says it's fine.
Once the cold sore has fully healed, wearing a lip balm with SPF 15 or above when you're outdoors in the sun can help lower the chance of the sun triggering another one.
Prone to cold sores? Pack an SPF 15+ lip balm for holidays and sunny days, and reapply it through the day.
The NHS recommends using a sunblock lip balm if you're prone to cold sores and plan to spend time outdoors in the sun.2 It's a simple, easy step that can cut down how often you get them.
Tip 4: Avoid spreading the virus while you heal
Cold sores are contagious from the moment you first feel tingling until the scab has fully healed and the skin underneath looks normal again.2 They're most infectious when the blisters burst, so that's when extra care matters most.
During an outbreak, avoid kissing anyone, especially babies and young children. Don't share anything that touches your mouth, like cups, cutlery, straws, lip balm or face towels.
Cold sore near your eye, or eyes becoming sore and red? See a GP or optician urgently.
Touching the cold sore and then other parts of your face can spread the virus to new places. Washing your hands after every application of cream really helps lower this risk.
Stress, tiredness and illness can all weaken the immune response that keeps the virus dormant between outbreaks. Looking after your sleep and general health won't stop cold sores completely, but it can make them less frequent.
Finding outbreaks frequent or particularly troublesome? Speak to your pharmacist about your options, including whether antiviral tablets might suit you better.
Frequently asked questions
When should I start using cold sore treatment?
As soon as you notice the first signs of a cold sore. This will typically be a tingling, itching or burning sensation on or around the lips. Antiviral creams such as aciclovir work best during this early prodromal stage, before any blisters appear. Starting treatment within the first 24 hours gives the best chance of reducing severity and shortening healing time.4
How long does a cold sore last with treatment?
With antiviral treatment started promptly, a cold sore typically heals within five to seven days. Without treatment, most cold sores resolve within seven to ten days. Treatment also tends to reduce the size of the blister and the level of discomfort during the outbreak.
How often should I apply cold sore cream?
Aciclovir 5% cold sore cream should be applied five times a day, every four hours. A suggested schedule is 7am, 11am, 3pm, 7pm, and 11pm.3 The standard course is five days, which can be extended to ten days if the sore hasn't healed.
Can I use cold sore cream on genital herpes?
No. Aciclovir cream licensed for cold sores is intended for use on the lips and face only. Genital herpes requires different treatment. If you think you have genital herpes, speak to your GP or visit a sexual health clinic for advice. Genital herpes treatment is also available through Pharmica.
Does cold sore cream still work once a blister has appeared?
It can help reduce symptoms and prevent blisters from worsening, but it is significantly less effective once blisters have fully formed. The best results come from applying it at the earliest tingling stage, before any visible blister appears.4
References
- World Health Organization. Herpes simplex virus. 2023. who.int
- NHS. Cold sores. nhs.uk
- National Center for Biotechnology Information / InformedHealth.org. How effective are creams and tablets for the treatment of cold sores? 2025. ncbi.nlm.nih.gov
- NHS. How and when to take or use aciclovir. nhs.uk
- Patient.info. Aciclovir cream. 2024. patient.info
- Illing PT et al. A Comprehensive Overview of Epidemiology, Pathogenesis and the Management of Herpes Labialis. Viruses. 2022. ncbi.nlm.nih.gov
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.