Cold sores are small fluid-filled blisters that appear on the skin, usually on the lips, chin, cheeks or in the nostrils. They are caused by a very common viral infection.
- Cold sores are caused by the herpes simplex virus.
- Infection is very common and is easily passed from person to person by close physical contact.
- The sores are raised, fluid-filled blisters and can be painful.
- Cold sores usually occur on the lips, chin, cheeks or in the nostrils. Occasionally they occur inside the mouth on the gums or roof of the mouth.
- A tingling or burning sensation is often present just before cold sores develop.
- Medicines can relieve some of the pain and discomfort.
What causes cold sores?
Cold sores are due to infection with the herpes simplex virus (HSV). There are two types of HSV.
- HSV-1 mainly causes oral and facial infections like cold sores.
- HSV-2 mainly causes genital and rectal infections (anogenital herpes).
The virus is spread by close physical contact.
What are the symptoms of cold sores?
The initial infection
When a person is infected with the herpes simplex virus for the first time, the episode is called a primary infection or initial infection. This usually happens when you are a child as a result of close contact (eg, kissing) with relatives who have the virus. It can take 1–3 weeks to show any symptoms.
Image credit: Canva
An infection outbreak has four stages:
- A tingling feeling in the skin.
- Over the next 48 hours, you may notice slight swelling of the area and then the development of a number of fluid-filled blisters, which are often painful.
- Over the next few days, the blisters burst and form clusters leaving fluid-filled sores.
- After 8–10 days, the sores eventually dry, scab over and heal without scarring. This stage can be irritating and painful.
You are contagious from the moment you first feel tingling or other signs of a cold sore coming on until the cold sores are completely covered by dry scabs.
What is the treatment for cold sores?
For most people with just one or two blisters on their lip or near their nose, keeping the blister clean, dry and leaving it alone are all that is needed. Below are some tips that can help with healing.
- Use sunblock lip balm (SPF 15 or above) if you’re outside in the sun.
- Cold sore patches can protect the skin while it heals.
- Ice, held against the blisters, or a warm wash cloth may help ease any pain.
- Avoid acidic or salty food if it makes your cold sore feel worse.
- Rinse your mouth with salt water or a pain relieving mouthwash.
- You can buy an antiviral cream called aciclovir from your Pharmacy. Read more about aciclovir cream.
- A kanuka honey based cream called Honeva is also available and has been shown to be as effective as aciclovir for treating cold sores.
- Take pain relief such as paracetamol or ibuprofen.
How can I prevent spreading cold sores to other people?
Hygiene is important for people infected with the herpes virus. To help prevent it spreading:
- do not kiss anyone while you have a cold sore, especially babies
- do not share anything that comes into contact with a cold sore (such as cold sore creams, towels, cutlery or lipstick)
- do not have oral sex until your cold sore completely heals as you could give your partner genital herpes
- do not touch your cold sores – if you do, wash your hands.
When to see your GP
See your GP if:
- the cold sore has not started to heal within 10 days
- you have an infection near the eye
- you're worried about a cold sore or think it might be something else
- the cold sore is very large or painful
- you have swollen, painful gums and sores in the mouth (gingivostomatitis)
- you have a weakened immune system – for example, because of chemotherapy or diabetes.
If the cold sores are very large, painful or keep coming back, your GP may give you an antiviral treatment like valaciclovir.
Can cold sores come back?
The herpes simplex virus remains hidden in your nerves for the rest of your life. It can become active again from time to time causing a cold sore. This will usually show up in the same places where you may have had a previous infection. Most people don't get more than one recurrence of cold sores per year, but about 5–10% of people experience 6 or more episodes per year. Situations that trigger the virus to become active include a fever (eg, a common cold), menstruation, trauma, UV radiation (exposure to sunlight), extreme tiredness or lowered immune function.
Some things you can do to take care of yourself when you have a cold sore include:
- Taking care to prevent the spread of the virus though good hygiene
- Avoiding anything that triggers your cold sores
- Using sunblock lip balm if you're outside in the sun
- Using treatments to help ease pain and swelling.
The following links provide further information about cold sores. Be aware that websites from other countries may have information that differs from Aotearoa New Zealand recommendations.
Facial herpes The NZ Herpes Foundation
Cold sores NHS Choices, UK
- Valaciclovir – a first line antiviral medicine BPAC, NZ, 2016
- Herpes simplex. DermNet NZ
- Antiviral preparations NZ Formulary
- Semprini A, Singer J, Braithwaite I, Shortt N, Thayabaran D, McConnell M, Weatherall M, Beasley R. Kanuka honey versus aciclovir for the topical treatment of herpes simplex labialis – a randomised controlled trial BMJ Open. 2019 May 14;9(5):e026201