Cold sores are common and relatively harmless in toddlers and children, but the cold sore virus can be dangerous for babies.

According to the American Academy of Pediatrics, many children will start to get cold sores by the age of 5. Newborns rarely get cold sores, but, when a baby who is less than 6 months old contracts the cold sore virus, it can have severe effects.

Babies can catch the cold sore virus through contact with a cold sore on another person. Therefore, people with a cold sore should avoid kissing babies or letting babies touch the sore.

If caregivers think that a baby may have come into contact with a cold sore, they should monitor the infant for any unusual behavior and contact a doctor to discuss the best course of action.

This article will take a close look at cold sores in newborns and infants, including the risks, treatment, and prevention.

Cold sores are tiny blisters that form on and around the lips, often at the edge. The blisters pop within a few days and turn into a crust. They disappear within a few weeks.

Cold sores are contagious and spread through close contact. This can include kissing and sharing cups, utensils, or towels.

When people get a cold sore, they may notice itching, tingling, or burning before the blisters become visible. Cold sores can spread at this stage, but they become most contagious when the blisters are visible.

The herpes simplex virus 1, known as HSV-1, is responsible for cold sores. This virus is similar to the virus that causes genital herpes, called HSV-2.

It is rare for newborn babies to get a cold sore because they still have their mother’s antibodies in their blood, which means that they share her immunity.

However, because the immune system of an infant under 6 months old will not yet be fully developed, if they do get a cold sore, this virus can have severe effects.

If a pregnant woman has genital herpes, the baby can get neonatal herpes through contact with fluids in the birth canal during vaginal delivery. This is the cause of almost 90 percent of neonatal cases, although babies can also contract the virus shortly after birth.

Babies can catch cold sores in two ways:

  • Vertical transmission. This occurs when the mother has genital herpes, and the infant catches the virus in the birth canal. This can happen even if the mother is not experiencing any symptoms. It is also possible for the infant to catch the disease through the placenta.
  • Horizontal transmission. This happens through contact after birth. People can be contagious without being aware and without visible symptoms. A kiss or a shared cup, toy, towel, or another object can all transmit the virus.

The mother cannot pass the infection to the newborn through breast milk.

However, HSV lesions can sometimes occur on other areas of the body besides the mouth. If they are present on the breast, HSV can be transmitted by direct contact with a sore or by feeding breast milk that has contacted the lesion.

If a person has HSV lesions on their breast, they should not feed their infant from that breast, nor give expressed breast milk from the affected breast.

While a herpes infection is not usually harmful in older children, newborns and babies can experience complications.

When children get their first cold sore, the symptoms may be more severe and can include a fever, sore throat, and blisters that spread beyond the lips and into the mouth.

Early symptoms of herpes infection in a newborn include:

  • a low-grade fever, which is 100.4°F
  • poor feeding
  • one or more small skin blisters

A newborn may then experience more severe symptoms such as:

  • a high fever
  • seizures
  • lethargy or going floppy

Cold sores pose the highest risk to infants during the first weeks of their lives. The herpes virus can cause severe problems at this stage and may even be fatal if it spreads to the organs, including the eyes, brain, or lungs.

People should see their doctor immediately if they suspect that a baby has a herpes infection.

Newborns who have developed herpes may need to spend 21 days in hospital receiving an intravenous antiviral medication.

For infants and children older than 4 weeks, treatment may not be necessary. HSV infection between 1 and 6 months of age is rare, but complications may be more likely. Any infant under 6 months with signs of, or concerns about, HSV infection should be seen by their doctor right away.

However, it is possible to manage cold sores by:

  • placing cold compresses on the blisters
  • taking pain relievers to minimize the discomfort
  • taking prescription antiviral medications in an ointment or pill form to speed up the healing process

It may also be beneficial for women with the virus to take prescription medication to avoid outbreaks of oral or genital herpes during pregnancy.

Once someone has contracted the herpes simplex virus, it will remain in their system for the rest of their life. Although there is no cure for the condition, children and adults can treat the symptoms when they arise.

It is not necessary for caregivers with cold sores to isolate themselves from babies, but they should avoid letting them come into contact with the sores. Once a cold sore turns scabby and dry, it is usually no longer contagious.

People with a cold sore can do the following to keep an infant safe:

  • washing the hands regularly and thoroughly, especially before touching the infant
  • covering the cold sore and not touching it, especially before or during contact with the infant
  • using separate towels, washcloths, cups, and utensils for the infant
  • avoiding kissing the infant
  • teaching older children to avoid kissing or sharing utensils or towels with people with cold sores
  • ensuring that infants and children do not rub their eyes if they have a cold sore

Newborns do not often get cold sores. However, during the early weeks of their lives, contact with cold sores can be dangerous. Medical attention is necessary.

Older infants will usually experience cold sores in the same way as children and adults, although the first outbreak can be more severe.

For babies over 6 months old, cold sores can be uncomfortable, but they are not serious and generally resolve within a few weeks.

Caregivers should take an infant to see a doctor if they are concerned about cold sores or related symptoms.