What is a cold sore?
Cold sores are caused by the herpes simplex virus (usually type 1, HSV-1), which most people are exposed to at some point, often in childhood. After the initial infection, the virus lies dormant in nerve tissue and can reactivate periodically, causing recurrent blisters around the lips and mouth.
Outbreaks are usually mild and self-limiting, resolving within one to two weeks, though they can be uncomfortable and cosmetically bothersome.
Triggers for reactivation
- Sun exposure to the lips — a very common trigger in Australia.
- Illness, fever, or a run-down immune system.
- Stress and lack of sleep.
- Hormonal changes, including around menstruation.
- Local trauma, such as dental work or lip injury.
Signs and symptoms
- A tingling, itching or burning sensation before blisters appear (the prodrome).
- Small, fluid-filled blisters, usually clustered on or near the lip border.
- Blisters that burst, crust over, and heal within 7–10 days.
- Recurrences typically appear in the same general area each time.
Diagnosis
Cold sores are usually diagnosed by their characteristic appearance and history of recurrence. Swabs are occasionally used if the diagnosis is unclear or the presentation is atypical.
Treatment options
Antiviral cream
Most effective when applied at the earliest tingling sign, before blisters fully form.
Oral antiviral medication
For more frequent or severe outbreaks, a short oral course can shorten the episode.
Suppressive therapy
For people with frequent recurrences, regular low-dose antiviral medication can reduce outbreak frequency.
Symptomatic care
Simple pain relief and keeping the area clean supports healing during an active outbreak.
Prevention
- Use a lip balm with SPF if sun exposure is a known trigger for you.
- Avoid touching or picking at active blisters, and wash your hands after applying treatment.
- Avoid close contact (including kissing) while blisters are active, as this is when the virus is most contagious.
- Manage stress and get adequate sleep where possible, if these are known triggers.
Frequently asked questions
Are cold sores contagious?
Yes, particularly while blisters are active and weeping. The virus spreads through direct contact, including kissing and sharing items like lip balm or cutlery.
Can cold sores be cured?
There's no cure — once you're exposed to HSV-1, the virus remains dormant in your body permanently. Treatment focuses on managing outbreaks and reducing their frequency and severity.
Why do I keep getting cold sores in the same spot?
The virus lies dormant in the nerve that supplies that area of skin, so reactivation tends to follow the same nerve pathway each time, producing outbreaks in a similar location.