Cold sores are caused by the herpes simplex virus. They appear as small tiny blisters filled with fluid. These are often at the edge of the lip. The blisters will then open, may weep and form a crust. They generally disappear in about 1 to 2 weeks.
There are 2 strains of the virus:
Usually HSV-1 strain causes cold sores to appear on the mouth. HSV-2 causes sores to appear on the genitals.
The herpes virus spreads by direct skin-to-skin contact. It is can be dangerous and even fatal for newborn babies (especially under 4 weeks of age).
Although HSV is more dangerous for babies under 4 weeks old, it can cause complications for older babies and children in rare situations. The most serious of these is called encephalitis. This is extremely rare, and happens when the virus causes an inflammation of the brain.
Immediate action required: Call 999 or 112 if your child has a cold sore and shows any of the symptoms of encephalitis:
- difficulty waking
- being very drowsy
- behaving very differently to how they usually behave
Blisters are the main symptom of cold sores.
Your child may have clusters of tiny blisters filled with fluids. They are usually inside the mouth, on the tongue and outside the mouth.
If your child sucks their fingers, you may also notice blisters on their fingers. These blisters will open and the fluid will ooze out. This will result in crusting forming on the affected area. The virus can also spread to their eyes, if your child touches an open sore and then rubs their eyes.
Contact your GP urgently if you see a blister near your child's eye
Other symptoms include:
- sore gums, sore throat and swollen glands
- more saliva than normal
- high temperature
- refusal to drink fluids
What to do
When you notice your child is developing a cold sore:
- talk to your pharmacist. They might recommend an antiviral cream. This speeds up the time the cold sore takes to heal. They might also recommend creams for the pain and irritation
- make sure your child drinks fluids such as water or milk regularly
- offer them cool soft foods to eat
- don't give them salty foods or citrus fruits as they might sting their mouth
- give your child a painkiller such as ibuprofen or paracetamol if they are in pain. Both are available in liquid form for young children
- avoid touching the affected areas. This could spread the virus.
- remind your child to wash their hands often in soap and warm water. Tell them not to touch their eyes
- use separate towels and wash your child’s clothes separately
- wash your hands to avoid the infection spreading. Don't forget to wash your hands before and after applying your child's cold sore cream
- don't share your child's creams or medications with other people. This can cause the infection to spread
- explain to adults and your child’s siblings to avoid kissing them if they have a cold sore
If your child is under 3 months old, or has asthma, check with your GP or pharmacist before giving them ibuprofen. Children under the age of 16 should not take aspirin
Non-urgent advice: Contact your GP if:
- your child's cold sore hasn't started to heal within 10 days
- the cold sore is very large or painful
- your child is refusing to drink fluids
- they also have swollen painful gums and sores in their mouth
- they have a weakened immune system. For example they have diabetes or are taking medication that affects their immune system
- you are pregnant and get a cold sore
- you're not sure if it is a cold sore or something else
- your child gets a cold sore on their eyelid or around their eyes
- your child's cold sores keeps coming back
Cold sores usually clear up without treatment in 7 to 10 days. They do not leave a scar. Cold sores often do not need any treatment.
Your child will be infectious for a least 1 week.
Childcare and school
Children usually continue attending childcare facilities and school when well enough to attend.
Children with cold sores should avoid contact sports until:
- there are no active lesions
- all blisters are crusted over
- they have had no systemic symptoms (for example, fever or malaise) for 72 hours
- there have been no new lesions for 72 hours