What is it?

Cold sores are small fluid-filled blisters that appear on the skin, most commonly in small children these are on the lips, chin, cheeks, or in the nostrils. Some people have no symptoms from the infection; others develop painful and unsightly cold sores that last for a week or more. Cold sores are caused by infection with the herpes simplex virus (HSV).

Not everyone who is exposed to the virus will develop symptoms, however the virus does stay in the body and there may be a re-occurrence of the symptoms, causing blisters in and around the mouth (cold sores).

How does it spread?

Small blisters containing clear fluid become very itchy and painful. When scratched this fluid often oozes from the sore/blister. The fluid from the blisters and the saliva are highly infectious and the infection can be passed onto others though direct contact or through contamination on toys or feeding utensils. The infection can also be passed on from individuals without symptoms.

Infectious period

The infectious period is around two weeks.

Cold sores are infectious until they go away completely. A person is most contagious when the sores are oozing fluid but the virus can still be passed on even when there are no active blisters.

What are the symptoms?

In addition to the cold sore blisters, children may display other symptoms. This includes fever, irritability, poor appetite, drinking less, excessive dribbling and sore swollen gums.


Image 1: https://www.healthnavigator.org.nz/health-a-z/c/cold-sores/ 

Image 2: https://www.plunket.org.nz/child-health-concerns-and-symptoms/skin-issues/cold-sores/#what-causes-cold-sores 


Exclusion period

A child with cold sores should stay home until the sores have crusted or healed, otherwise other children may also be infected.

Children should also be well enough to take part in activities without requiring one-on-one attention from teachers.

Responsibilities of Early Childhood Education Service

Children may remain infectious for several weeks after this illness so attention to hygiene is important.

  • Tell parents that a child at the centre has cold sores.
  • Display information about cold sores prominently at your centre and provide each family with a copy of this factsheet.
  • Make sure staff and children’s hands are washed often with soap and warm water and are thoroughly dried. Pay particular care to the infants.
  • Clean all toys and surfaces with detergent, and then disinfect by wiping with or soaking in a diluted bleach solution. Disinfecting toys and general surfaces such as tables is a precaution for outbreaks, not a ‘normal’ procedure. When you don’t have an outbreak frequent washing with detergent is okay.

Make up a new bleach solution daily. Check on your bottle of bleach for the percentage of sodium hypochlorite, and make up as per table below.

Strength of bottleBleach (ml)Water (ml)Total (ml)
  • Toys that children suck or chew should be cleaned in the dishwasher or washing machine
  • Discourage sharing of food, drink and other utensils.
  • Keep all bed linen, towels, face cloths and feeding equipment separate for each child and wash regularly.
  • Keep all comfort blankets, toys and pacifiers separate for each child.

Responsibilities of parents

  • Keep your child home until the sores have crusted or healed.
  • Take comforters home each day and clean.
  • See your GP or contact Healthline on 0800 611 116 straight away if the cold sores are near the eyes.
  • See your GP if your child is showing signs of dehydration – dry mouth and tongue, sunken eyes, cold hands and feet, unusual sleepiness or lack of energy or passing less urine that normal.


For some people with just one or two blisters on or near the lip or nose, keeping the sores clean and dry may be all that is needed. Other treatment options are listed below:

  • See your GP or Pharmacist for treatment such as cold sore creams and pain relief.
  • Wash hands thoroughly before or after applying cream or other treatments to the affected area.
  • Ice or warm cloth, held against the blister may help ease pain.
  • If blisters are in the mouth, cold water or ice-blocks may help relieve pain.
  • Take regular pain relief if pain is stopping child from eating or drinking.

For more information




Download printable factsheet

Last updated 14 July 2022.