Cold sores are common, painful and almost always caused by the herpes simplex virus type 1. Most people first catch the virus in childhood; it then lies dormant and flares up from time to time, often triggered by stress, illness, sunlight or a run-down immune system.

The good news is that most cold sores heal on their own within seven to ten days without any treatment at all. What you buy at the pharmacy is mostly aimed at shortening an episode by a day or two, easing pain, or hiding the blister while it heals.

How the pharmacy shelf is organised

Walk into any UK pharmacy and you will usually see three types of cold sore product next to each other.

Antiviral creams. The active ingredient is usually aciclovir 5% or penciclovir 1%. Applied five times a day at the very first tingle, they can shorten an episode slightly. They do not prevent the blister from forming once it has already broken out. Common brand names include Zovirax and Fenistil. Generic aciclovir is typically cheaper and the same medicine.

Hydrocolloid patches. Small clear patches such as Compeed Invisible cover the blister, speed healing and reduce the risk of spreading the virus to others. They also make the sore less visible. They contain no active antiviral.

Numbing and drying products. Lip balms containing lidocaine, zinc sulphate or tannic acid aim to ease pain or dry out the blister. Evidence is mixed but many people find them soothing.

What the pharmacist will ask

Before handing anything over, a pharmacist will usually check:

• How often you get cold sores and whether the pattern has changed.
• Whether you are pregnant, breastfeeding, or have a weakened immune system.
• Whether this is actually a cold sore, or something else such as impetigo, angular cheilitis, or an allergic reaction.
• Whether the blister is near your eye — anything close to the eye should be assessed by a GP or optician urgently because of the risk of corneal involvement.

Who qualifies for prescription-only options

For most adults with a typical cold sore on the lip, the counter products above are the first line. Oral antivirals such as aciclovir 200 mg tablets or valaciclovir are prescription-only in the UK. A GP may prescribe them for:

• People with frequent, severe outbreaks where counter creams have not helped.
• People who are immunocompromised, including some cancer patients and those on immunosuppressive therapy.
• Widespread outbreaks, eczema herpeticum, or sores spreading beyond the lip.

Oral antivirals are not available through the NHS Pharmacy First service for cold sores at the time of writing. A referral to a GP or an NHS 111 service is needed.

When to stop trying to self-treat

Seek further advice if:

• The sore has not healed after ten to fourteen days.
• You get cold sores more than six times a year.
• The sore is very painful, spreading, or weeping heavily.
• It is close to or inside the eye.
• You have a weakened immune system, are a young baby, or are pregnant.
• You develop a fever or feel generally unwell.

Preventing the next one

Most outbreaks cannot be prevented entirely, but you can reduce frequency by using an SPF 30+ lip balm when out in strong sun, not sharing towels or lip products, and looking after general health and sleep. Carrying a tube of aciclovir cream means you can start treatment at the very first tingle, which is when it is most likely to help.

Finding a pharmacy nearby

You can find your nearest community pharmacy, including weekend and late opening hours, using PharmSee's pharmacy directory. If you need help outside normal hours, NHS 111 can direct you to an open pharmacy or urgent service.

Sources

• NHS: Cold sores
• NICE Clinical Knowledge Summaries: Herpes simplex, oral
• British National Formulary: aciclovir, penciclovir
• Community Pharmacy England: Pharmacy First service specification