How Long does a Cold Sore Last and How to Treat it

It starts as a tingle — that unmistakable itch on the edge of your lip that makes your heart sink, because you know exactly what’s coming. Within a day there’s a blister, within two it’s a full-blown cold sore, and you’re cancelling nothing but feeling self-conscious about everything. Cold sores are absurdly common (most adults carry the virus), mildly miserable, and surrounded by folk remedies of wildly varying usefulness. Here’s how long a cold sore actually lasts, how to treat it properly, and how to stop the next one.

How Long Does a Cold Sore Last?

A typical cold sore runs its course in 7–10 days without treatment. It follows a predictable pattern:

• Days 1–2 (tingling stage): itching, burning, or tingling around the lips. No visible sore yet — this is the golden window for treatment.
• Days 2–4 (blister stage): small fluid-filled blisters appear, often clustered. This is when it’s most contagious.
• Days 4–6 (weeping/ulcer stage): blisters burst, leaving a shallow, sore ulcer. Still contagious. The least attractive phase, if we’re honest.
• Days 7–10 (scabbing/healing): a scab forms, then flakes away. The skin underneath may look pink for a few days but the virus retreats back into dormancy.

With prompt antiviral treatment, you can often cut this to 4–5 days — or occasionally stop the sore developing at all if you catch the tingle early enough. The NHS page on cold sores confirms the timeline and when to seek help.

How to Treat a Cold Sore: What Works

Antiviral creams (the main event)

Aciclovir cream (Zovirax and pharmacy own-brands, around £4–£6) is the standard treatment. It doesn’t kill the virus — nothing does — but it stops it replicating, which shortens the outbreak. The critical factor is timing: start at the first tingle for the best effect. Once blisters are fully formed, it helps less, though it’s still worth using. Apply five times a day for 4–5 days. Penciclovir (Fenistip) is an alternative applied every two hours while awake — some people find it more effective, though it’s pricier.

Antiviral tablets

For severe, frequent, or slow-healing cold sores, your GP or pharmacist can provide aciclovir or valaciclovir tablets, which work systemically and are more effective than creams. If you get cold sores very frequently (say, monthly), ask about suppressive therapy — a daily low dose that can dramatically reduce outbreaks.

Pain relief and comfort

Paracetamol or ibuprofen for soreness. Keep the area clean, don’t pick the scab (it delays healing and risks bacterial infection), and avoid acidic or salty foods that sting. A cold compress can soothe the throbbing. Lip balm with SPF is worth using once healed — sun is a known trigger.

What about the folk remedies?

Tea tree oil, aloe vera, ice, toothpaste, lemon balm — the evidence for all of these is thin to nonexistent. Some (like toothpaste) can irritate the skin and make things worse. Lysine supplements have mixed evidence at best. My take: spend your money on the antiviral cream that actually works rather than experimenting with the bathroom cabinet.

Are Cold Sores Contagious? (Yes — Here’s How to Avoid Spreading Them)

Cold sores are caused by herpes simplex virus type 1 (HSV-1), and they’re contagious from the tingle until fully healed. Practical precautions:

• Don’t kiss anyone — especially newborn babies, pregnant women, and people with weakened immune systems (the virus can be serious for them)
• Don’t share towels, cutlery, lip balm, or razors
• Wash your hands before and after touching the sore
• Avoid oral sex during an outbreak — HSV-1 can cause genital herpes
• Don’t touch your eyes after touching the sore (it can cause eye infections)

Once the scab has fallen off and the skin looks normal, you’re no longer contagious.

How to Prevent Cold Sores Coming Back

The virus stays in your body for life, hiding in nerve cells. Outbreaks are triggered by:

• Sunlight — use SPF lip balm daily, not just on holiday
• Stress and illness — when your immune system dips, the virus seizes its chance. Keeping generally healthy helps: our guide to boosting your immune system in winter covers the foundations, and managing stress and anxiety matters more than people realise
• Chapped, damaged lips — keep lips moisturised; cracked skin is an open door
• Hormonal changes — some women get them with their cycle; not much to be done except treating promptly

When to See a GP or Pharmacist

Most cold sores don’t need a doctor. But seek advice if:

• The sore hasn’t started healing after 10 days
• You get them very frequently or they’re unusually large/painful
• They spread to your eyes (pain, grittiness, light sensitivity — see a doctor urgently)
• You have a weakened immune system
• Your baby or young child gets a cold sore (babies under 6 months with a cold sore need prompt medical attention)

Cold Sores vs Other Lip Problems: Telling Them Apart

Not every lip blister is a cold sore. Here is how to tell:

• Cold sore (HSV-1): tingling first, then clustered blisters on or around the lip edge, weeping, then scabbing. Recurs in the same spot. Contagious.
• Impetigo: honey-coloured crusts, often around nose and mouth, common in children. Bacterial — needs antibiotic cream, not antiviral. More crusty than blistery.
• Angular cheilitis: cracked, sore corners of the mouth — not blisters. Usually fungal or bacterial, or related to drooling, dentures, or vitamin B deficiency. Antifungal cream, not aciclovir.
• Chapped lips: dry, flaky, cracked all over — no blisters, no tingling prodrome. Lip balm and hydration, not antivirals.
• Allergic reaction: swelling and itching after a new lip product — no blisters, resolves when you stop the product.

If your “cold sores” do not follow the classic tingle-blister-scab pattern, do not respond to antiviral cream, or keep recurring in odd places, get a pharmacist or GP to take a look. Treating the wrong condition wastes time and money — and a quick professional opinion is free. Pharmacists in particular are underused for this: they see lip problems daily and will tell you straight if it is not a cold sore.

The realistic takeaway: you can’t cure cold sores, but you can absolutely tame them. Keep antiviral cream in the house so you can strike at the tingle stage, protect your lips from sun and cracking, and don’t let embarrassment stop you treating them promptly. Seven to ten days feels like forever when it’s on your face — but with the right approach, most outbreaks are a minor nuisance rather than a fortnight-long ordeal.