What are cold sores?

Cold sores are small blisters on the skin, often around the mouth. They are caused by herpes simplex virus (HSV).

What is HSV?

The herpes simplex virus (HSV) is a very common virus that is spread through direct contact with the skin, saliva, or genitals of an infected person. There is no cure for HSV, so once you have the virus, it will stay in your body for life.

What are the symptoms of HSV?

HSV does not always cause symptoms, so you can carry it without knowing it.

There are two main types of HSV:

• HSV-1 (type 1) commonly causes cold sores on the face and lips, and sometimes on the genitals. Around 4 in every 5 Australian adults have this type.
• HSV-2 (type 2) causes mostly genital herpes — sores around the genitals or anus, and usually spreads during sexual contact. Around 1 in 8 sexually active Australians has genital herpes.

Will cold sores or genital herpes affect my pregnancy?

If you have had cold sores before, it is quite common to have an outbreak during pregnancy, even if you haven't had one for a long time. If you are infected with HSV for the first time early in your pregnancy, it may lead to miscarriage.

Cold sores do not usually affect your unborn baby, but they are uncomfortable and infectious. While you're pregnant, or if have a health condition that affects how your immune system works, HSV can cause severe illness.

If you have genital herpes, the virus may transfer to your baby during a vaginal birth. If it is your first outbreak, your baby may be more at risk. This is because your body hasn't had time to develop immune protection against the virus, which also helps protect your baby.

If you have a genital herpes blister when you give birth, or if your first infection occurs within the last 6 weeks of pregnancy, your doctor may recommend a caesarean. This can help prevent the herpes virus passing from you to your baby during a vaginal birth.

When should I see my doctor?

If you have HSV and you become pregnant, or if you develop cold sores or genital herpes during pregnancy, it's important to speak with your doctor or midwife, and discuss your treatment options. Together, you can plan how to manage your symptoms during pregnancy.

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How are cold sores treated during pregnancy or breastfeeding?

You can treat cold sores with aciclovir cream — an antiviral cream that you can buy from a pharmacist without a prescription. You apply this to cold sores directly. Ask your pharmacist for advice on how to apply this cream.

If your symptoms are painful, your doctor can prescribe aciclovir or valaciclovir tablets. These antiviral medicines are thought to be safe during pregnancy and breastfeeding. Famciclovir tablets are not recommended during pregnancy.

Always speak to your doctor before taking any medication when you are pregnant.

How do I protect my baby from herpes?

A newborn baby can be infected with HSV from a kiss or a touch from someone with cold sores, or during vaginal birth (if you have a genital sore at the time your baby is born).

The risk of you spreading genital herpes to your baby during pregnancy is low, and most babies born to mothers who carry the virus are not affected. Sometimes, HSV can cause serious problems for a baby, such as infections to the eyes and throat, damage to the nerves, and in rare cases, death. Talk to your doctor or midwife about the best course of action for your situation.

If you or your partner has a cold sore or genital herpes, ask your doctor how you can best manage it during the pregnancy and after the birth. This will lower the risk of passing the virus to your baby.

It's important to maintain strict hygiene habits when caring for a new baby. If you, or anyone in close contact with the baby has cold sores, help prevent spreading the virus by:

• covering cold sores when you are around your baby
• avoiding kissing your baby until the sores have completely healed
• avoiding touching the cold sores with your hands
• washing your hands thoroughly before touching your baby
• asking any relatives with cold sores to avoid touching or kissing your baby

What if I have a cold sore while breastfeeding?

If you have cold sores, it is safe to breastfeed your baby as long as the sores are not on the breast or nipple. If they are, you should temporarily stop breastfeeding from the affected breast until the sores have cleared up.

You should express and dispose of breastmilk from the affected breast. Breastmilk can be contaminated if it comes in contact with the skin lesions. Talk to your doctor or midwife as soon as you notice a cold sore on your breast or nipple.

Complications of HSV and what happens if my baby gets a cold sore?

If you think your baby is developing a cold sore, show your doctor or midwife as soon as you can. Signs of HSV infection include:

• blisters on the skin
• fever
• seizures
• tiredness
• poor feeding

These signs also happen in many other health conditions, but if you think your baby might have HSV, don't wait to see if they get better — seek medical help. Let the medical staff know if you or your partner have ever been diagnosed with HSV, have a cold sore or genital herpes.

Resources and support

If you are worried about your baby, see a doctor or midwife, or take them to the hospital.

• Read the Royal Hospital for Women fact sheet on Cold Sores in Pregnancy and Breastfeeding.
• Call Family Planning NSW Talkline on 1300 658 886 (Monday to Friday, 8:00am-8:00pm) or visit your nearest Family Planning NSW clinic.