A mum said her newborn baby "nearly died" from a kiss, after she was infected with a virus caused by a cold sore.
Mum-of-four Lynette Clare, 35, was told her five-day-old daughter Chloe Clare "might not live through the night" after she suddenly became critically ill.
Clare, from Cheshire, later discovered Chloe had contracted Herpes Simplex Virus (HSV-1) – the virus linked to cold sores.
"I had no idea cold sores could be so dangerous to newborn babies and there just isn't that awareness at all, but there desperately needs to be," Clare said.
Clare, who is also mum to Daniel, 18, Natalie, 16, and Jamie, nine, gave birth to Chloe at Warrington Hospital on 12 March 2013.
Five days later on 17 March she returned to the hospital for Chloe's heel prick test and noticed her daughter was unusually sleepy.
At 7.30pm, Chloe's temperature had increased to 42°C but her hands and feet felt cold, so Clare rushed her to A&E.
Within hours Chloe was in a high dependency unit. Doctors told Clare her daughter "might not make it through the night".
A consultant said Chloe had contracted HSV-1 encephalitis. Clare said she was kissed by a family friend who had a cold sore just days earlier.
Chloe was given antiviral medication and spent three weeks in hospital before making a full recovery.
"When the doctors told me Chloe might not make it through the night I was just devastated," Clare said.
"I thought I was going to lose her and stayed up with her all through the night.
"Luckily, when the consultant worked out it must have been linked to a cold sore she was put on antivirals and responded well to them.
"I just feel so lucky it was caught at the right time – I was told afterwards if I had waited until the morning before taking her into hospital she probably wouldn't be here today.
"None of the midwives on the maternity ward had warned me about cold sores being a risk, I just had no idea they were dangerous in any way.
"I think there should be something given out in the packs which are given to new mums.
"It is completely natural to want to kiss a newborn baby, you just want to shower them with love and kisses.
"How were we to know a cold sore could have caused this?"
Chloe, now three, is doing well, but has been diagnosed with microcephaly – an abnormal smallness of the head – which doctors believe is linked to the HSV-1.
She also has some speech problems and other minor developmental delays, but Clare said medics do not know if she would have developed these regardless of contracting the virus.
"Parents just have to know about this and if I can save at least one other family from going through the same thing then it has all been worth it," Clare added.
"I nearly lost my daughter and what I went through that first night is something no parent should have to go through.
"As a parent no one can ever prepare you to hear a consultant say your five-day-old baby might not make it through the night.
"It's a nightmare that never goes away."
Clare is campaigning to raise awareness of the condition with fellow mum Claire Henderson, from Doncaster, whose own daughter Brooke was hospitalised in September 2015 after sores appeared on her face, throat and lips.
Doctors discovered Brooke had developed HSV-1 after being kissed by a visitor with a cold sore and she was treated on an antiviral drip in hospital for five days.
Henderson, 33, has launched a petition calling on the Government to provide new parents with information on the dangers of cold sores to newborn babies, which so far has nearly 1,000 signatures at the time of writing.