A cold sore starts with tingling at the lip and turns into a blister — and once you have had one, it tends to come back. The NHS says cold sores should start to heal within 10 days, and are contagious from the first tingling until they have completely healed. Use antiviral cream as soon as you notice the early tingling. This sets out the NHS page “Cold sores”.
1. Antiviral cream at the first tingle. It does not always work once blisters appear, the page says.
2. No kissing until fully healed. Especially babies — it can cause neonatal herpes.
3. Not starting to heal within 10 days? See a GP. The same with a weakened immune system.
How it progresses — NHS
| Stage | What the NHS says | What to do (NHS) |
|---|---|---|
| 1. Start | A tingling, itching or burning feeling | Antiviral cream now |
| 2. Blisters | Over the next 48 hours, one or more painful blisters on the face | Don’t touch; dab cream, don’t rub |
| 3. Scab | The blisters burst and crust over | Still contagious until fully healed |
| 4. Healing | Should start to heal within 10 days | Not healing after 10 days: see a GP |
Do — NHS
- Avoid known triggers, such as sunbeds
- Use a sunblock lip balm of SPF 15 or above in the sun
- Paracetamol or ibuprofen for pain and swelling — no aspirin for children under 16
- Drink plenty of fluids to avoid dehydration
Don’t — NHS
- Don’t touch the cold sore except to apply cream — wash your hands before and after if you do
- Don’t rub cream in — dab it on
- Don’t eat acidic or salty food if it makes it feel worse
- Don’t kiss anyone until it has completely healed
- Don’t have oral sex until it has completely healed — you could give your partner genital herpes
How to wash your hands is in handwashing for 20 seconds. Paracetamol is the UK name; in Korea it is usually called acetaminophen (our gloss).
From a pharmacy — three things
| What | Use the NHS gives | Worth noting (our gloss) |
|---|---|---|
| Pain-relief cream | Eases pain and irritation | Not an antiviral |
| Antiviral cream | Speeds up healing — at the first tingle | Not always effective after blisters (NHS) |
| Cold sore patch | Protects the skin while it heals | A cover |
Why they come back
The NHS says most people are exposed to the virus in childhood through close skin contact such as kissing, and once infected the virus stays in the skin for life, sometimes causing a cold sore. Illness, sunshine or having a period can trigger one. Cold sores spread easily to other people and to other parts of your body.
When to see a GP
- It has not started to heal within 10 days
- You have a weakened immune system
Newborns, pregnant women and people with weakened immune systems may be referred to hospital. Kissing a baby when you have a cold sore can cause neonatal herpes, which is very dangerous for newborns. For fever in babies, see baby fever.
Checklist
- ☐ Antiviral cream at the first tingle, dabbed on
- ☐ No kissing until fully healed — especially babies
- ☐ Wash hands after touching it
- ☐ SPF 15+ lip balm in the sun
- ☐ Not healing within 10 days, or a weakened immune system? See a GP
Questions that remain
Can sharing cups or cutlery spread it?
The NHS page read here does not cover sharing items, so we say nothing about it.
Are there tablets?
The NHS page lists pharmacy creams, patches and painkillers only; it does not cover antiviral tablets, so we give none.
White ulcers inside the cheeks or lips are not cold sores and are not contagious, the NHS says (mouth ulcers).
Sources
- NHS — Cold sores — original (page last reviewed 19 February 2024, next review due 19 February 2027; checked 12 October 2026). Tingling, 48 hours, 10 days, contagious from first tingle until healed, when to use antiviral cream, four dos (SPF 15), five don’ts, three pharmacy items, childhood infection for life, triggers, neonatal herpes, GP and hospital.
- Not read. Korean agencies’ cold sore guidance; sources on antiviral tablets.
- Added by us. The “worth noting” column and the medicine naming note.
Where to check further
- A pharmacy — antiviral cream and patches.
Written 12 October 2026. The content follows the NHS original; the glosses are ours.