Cold sores are small, painful blisters caused most often by herpes simplex virus type 1. The virus remains in the body after infection and may reactivate. Outbreaks often begin with tingling, itching or burning before blisters appear around the lips or mouth.
How cold sores spread
The virus spreads through close contact with infected skin, saliva or sores. It can be passed on from the first tingling until the area has completely healed, and sometimes when no sore is visible. Touching a cold sore can also spread infection to the eyes, fingers or genitals.
Self-care
- Wash hands before and after touching the area.
- Avoid picking the sore and apply creams by gently dabbing.
- Do not share lip products, cups, cutlery or towels during an outbreak.
- Avoid kissing and oral sex until the sore has fully healed.
- Use lip balm with sun protection if sunlight is a trigger.
A pharmacist can advise about pain relief and antiviral cream. Antiviral treatment works best when started at the tingling stage. People with frequent or severe outbreaks may be prescribed antiviral tablets.
Protecting babies and vulnerable people
Do not kiss a newborn baby when you have a current cold sore. Neonatal herpes can be very serious. Avoid close contact with people who have severe eczema or a weakened immune system until the lesion has healed.
When to seek medical advice
Seek advice if a sore has not begun to heal within about ten days, is unusually large or painful, repeatedly returns, occurs inside the mouth with widespread ulcers, or you have a weakened immune system. A first episode during pregnancy or genital symptoms also deserves professional advice.
When to seek urgent help
Urgent assessment is needed for eye pain, redness, light sensitivity, blurred vision or sores near the eye. Seek immediate care if a newborn may have been exposed and becomes unwell, develops blisters, feeds poorly or is unusually sleepy.
Sources
Reviewed: 28 August 2026