Cold Sores and Babies

When to get help

NHS guidance on neonatal herpes asks you to call a GP or NHS 111 straight away if your baby is irritable and will not settle, is not feeding as well as usual, has a high temperature of 38C or more, or has a rash or sores on their skin, eyes or inside their mouth. It describes these as early warning signs that your baby is unwell and may need urgent treatment.

It asks you to call 999 immediately if your baby is lacking in energy, described as lethargic and listless; has a rash that does not fade when a glass is rolled over it, noting that a rash will not always develop and may be harder to see on brown and black skin; is becoming floppy; is not responding to you in their normal way; is difficult to wake from sleep; is breathing rapidly, has difficulty breathing, or makes noises when breathing such as grunting; has a seizure; is peeing less than normal; is crying constantly and cannot be soothed or distracted, or their cry does not sound like their normal cry; or has a blue tongue or skin, which on brown or black skin may be easier to see on the lips, tongue and gums, under the nails and around the eyes.

The same guidance adds a warning that explains the urgency: very often the baby will not have any specific herpes symptoms, such as a rash or blisters, but they can become unwell very quickly, so you need to act fast.

The 38C figure lines up with NICE guideline NG143 on fever in under 5s, which states that children younger than 3 months with a temperature of 38C or higher are in a high-risk group for serious illness.

How a baby catches it

NHS guidance explains that the herpes simplex virus can be passed to a baby through a cold sore if a person has a cold sore and kisses the baby. It can also be spread if a mother has a blister caused by herpes on her breast and feeds the baby from the affected breast or with expressed milk from it, and blisters on the fingers caused by herpetic whitlow may also spread the virus.

Transmission can also occur during birth. NHS guidance states that if you have genital herpes for the first time in your third trimester, particularly during the last six weeks, your newborn baby is at risk of catching herpes, with a risk of passing it on during a vaginal birth, and that the risk is much lower if you have previously had genital herpes or were infected for the first time in early pregnancy.

The window of highest risk

NHS guidance states that it is thought your baby can be most at risk of getting a herpes infection in the first six weeks after birth. The American Academy of Pediatrics describes the virus as dangerous to babies under six months of age, especially newborns within the first few months of life, and advises that parents or relatives with active cold sores should be especially careful not to kiss babies.

What to ask visitors to do

NHS guidance gives a specific set of precautions for the first weeks. Everyone should wash their hands before handling your baby. Discourage anyone who is not a close family member or carer from kissing your baby. The safest place to kiss your baby is on the top of their head, and kissing your baby near their mouth, nose or eyes should be avoided. People with a current cold sore, or a recent history of cold sores, should not kiss your baby. People with a known herpes infection, such as a cold sore or herpes blister, should avoid touching your baby unless they are a close family member or carer, and in that case they should carefully wash their hands first.

This is often socially awkward to enforce, and it is easier to state as a household rule set before visitors arrive than as an intervention in the moment.

If you get a cold sore yourself

NHS guidance sets out what to do if you develop a cold sore or any signs of a herpes infection: do not kiss any babies; wash your hands before contact with a baby; wash your hands before breastfeeding; if you develop any blisters on your breast, do not feed from it until all the blisters are healed; and cover up any cold sores, lesions or signs of a herpes infection anywhere on your body to avoid passing on the virus.

Breastfeeding continues normally unless there are sores on the breast itself. NHS guidance notes that you can breastfeed your baby while they are receiving treatment for neonatal herpes, unless you have herpes sores around your nipples.

Cold sores in an older baby or toddler

Once past the newborn period, a first herpes infection in a child usually presents differently. NHS guidance on cold sores asks you to see a GP if you or your child also have swollen, painful gums and sores in the mouth, which is gingivostomatitis, and this is the common form of a first infection in a young child. It can make eating and drinking painful, so watch for reduced fluid intake and signs of dehydration.

NHS guidance on cold sores also advises seeing a GP if a cold sore has not started to heal within 10 days, if you are worried about it or think it is something else, if it is very large or painful, or if there is a weakened immune system. It adds that newborn babies, pregnant women and people with a weakened immune system may be referred to hospital for advice or treatment.

The AAP flags two further situations for urgent attention: sores or blisters developing near the eyes, because the virus is a common cause of corneal infection; and a headache combined with confusion, seizure or fever during an outbreak, which could signal a brain infection such as meningitis or encephalitis.

Treatment

NHS guidance says neonatal herpes is usually treated with antiviral medicines given directly into the baby's vein, that this treatment may be needed for several weeks, and that related complications such as seizures will also need treating. For ordinary cold sores in adults and older children, a pharmacist can recommend creams to ease pain and irritation, antiviral creams to speed up healing and cold sore patches, and antiviral tablets may be prescribed for sores that are very large, painful or recurrent. Australia's healthdirect service gives comparable advice. This page gives no medicine amounts; follow the packaging or ask a pharmacist.