The tingle is the moment, not the blister
Hours before any blister appears, most people notice itching, stinging or tingling at one particular spot on the lip. That phase is called the prodrome, and it is the best moment to act: antiviral creams work better the sooner they go on after those first symptoms, not once the blister has formed. Wait until you can see the sore and the outbreak will run almost exactly as long as it would have anyway.
Cold sores are caused by herpes simplex virus type 1 (HSV-1), passed on through contact with the skin or saliva of someone with an active sore — or, in some cases, with no visible sore at all. The World Health Organization estimates that two in three people under 50 worldwide carry this virus, most of them since childhood. Once it is in, it isn’t cleared: it stays dormant in a nerve ganglion in the face and reactivates from time to time.
What you can buy at the pharmacy
| Product | What it does | When to use it |
|---|---|---|
| Aciclovir or penciclovir cream | Topical antiviral; shortens the outbreak if applied early | From the first tingle, five times a day |
| Hydrocolloid patch | Protects the sore, hides it and stops you touching it | From the moment the blister appears |
| Oral painkiller (paracetamol or ibuprofen) | Eases pain and inflammation | If it hurts to eat or talk |
| Lip balm with sun protection | Removes a common trigger | Daily, especially at the beach or in the mountains |
None of these clears the virus from your body: they all act on the active outbreak, not on the underlying infection.
How to apply the antiviral cream properly
The product information for aciclovir creams authorised in Spain says that adults and children over 12 should apply a thin layer to the affected area five times a day, roughly every four hours, skipping the overnight application. Treatment runs for 5 days; if the sore hasn’t fully healed, it can be extended to a total of 10 days. If it still isn’t improving at that point, it’s time to get it looked at.
A few details that make the difference:
- Wash your hands before and after applying it, so you don’t spread the virus to other parts of your own skin or pass it to anyone else.
- Don’t apply it inside the mouth, in the eyes or in the vagina: it can irritate mucous membranes.
- Use a cotton bud or a clean fingertip, never the same finger you then touch other parts of your body with.
- If your immune system is suppressed (on chemotherapy, say, or after a transplant), check with your doctor or pharmacist rather than treating it yourself.
- If you are pregnant or breastfeeding, ask before using any topical antiviral.
Why it keeps coming back in the same spot
HSV-1 travels along the nerve to a ganglion near where it first got in, and stays there dormant for the rest of your life. When it reactivates, it runs back down the same nerve to the skin or the lip, which is why the outbreak tends to appear in the same place every time. The most frequently cited triggers are:
- Sun exposure without lip protection.
- A fever or an infection (hence the old name “fever blister”).
- Physical or emotional stress.
- Hormonal changes, including menstruation.
- Tiredness and a dip in immune defences.
Not everyone who carries the virus gets outbreaks: many people are infected as children without ever developing a visible sore, and others have only one or two episodes in a lifetime.
How to avoid passing it on during an outbreak
The virus spreads most easily when there is an open or weeping sore, but it can also spread with no visible symptoms. While the outbreak lasts:
- Don’t share glasses, cutlery, towels or lip cosmetics.
- Avoid kissing anyone, especially babies and people with weakened immune systems.
- Don’t touch your eyes after touching the sore: the virus can cause a serious eye infection if it reaches the cornea.
- Avoid oral sex while the sore is active, since HSV-1 can be passed to the genital area.
Two things people get wrong
A couple of common beliefs are worth clearing up. First: “I’ve never had one, so I don’t have it.” The infection can stay latent for life without ever producing a visible symptom, so having no outbreaks doesn’t mean you aren’t a carrier. Second: “the more cream I put on, the faster it heals.” Going beyond the stated frequency or duration doesn’t speed up healing, and it does increase the risk of irritating the skin.
When to see a doctor
Speak to your doctor or pharmacist if any of the following happens:
- The sore doesn’t improve after 10 days of correct treatment, or is still there after two weeks without treatment.
- It appears near the eye, or you notice redness, pain or changes in your vision: that is an ophthalmological emergency.
- You have a high fever, very swollen glands, or the sore is spreading noticeably across the face.
- You get more than six outbreaks a year.
- You are on immunosuppressive treatment, have a condition that weakens your defences, or the outbreak appears in a newborn baby.
- You notice signs of a bacterial infection on top: the area gets redder, swells, or weeps pus instead of clear fluid.
- It’s the first time you’ve had symptoms like this and you want the diagnosis confirmed, particularly in small children, whose first episodes are sometimes mistaken for teething or other mouth complaints.
This article is for information only and does not replace assessment by a healthcare professional. If you have any doubt about your own case, speak to your doctor or pharmacist.
Sources: Product information and patient leaflet, Aciclovir VIR 50 mg/g cream — CIMA, AEMPS (in Spanish), Oral herpes — MedlinePlus, US National Library of Medicine (NIH), Herpes simplex virus — World Health Organization.