When pregnant Victoria Birtwistle noticed itchy bumps on her belly and hips, she presumed they were insect bites.
She visited her GP and obstetrician and they also believed the bumps were just a cluster of stings.
But what was thought to be harmless turned out to be terrifyingly dangerous and Victoria, 38, from Middleton, Greater Manchester, passed on a herpes virus which led to her unborn baby developing meningitis and later cerebral palsy.
It wasn't until her son Lucas, now six, was born that she discovered she had caught the cold sore virus and and passed it on to her unborn baby.
Victoria recalled: "When I first saw the rash they looked like horsefly bites and I was just given cream for them.
"I didn't have any other symptoms. I suppose I felt quite tired but I was heavily pregnant and I had developed high blood pressure so it seemed natural I wouldn't feel great."
It was only when Lucas came home from hospital that Victoria began to fear the worse. He let out a blood-curdling screams and turned blue several times before doctors realised he was suffering with seizures.
What Victoria didn't know was that the sudden shrieks were a sign of infant seizure.
Lucas was transferred to North Manchester General Hospital where he would spend the following 10 weeks. After extensive tests, doctors discovered the little boy had traces of the HSV-1 virus - or cold sore virus - in his body.
Victoria said: "I was totally shocked. How could a newborn have caught the cold sore virus within hours of birth? Not only that, but I'd never had a cold sore in my life."
But the doctor's diagnosis prompted Victoria to remember the strange rash that had developed several weeks previously.
Doctors then concluded that the small red blisters that had spread across the lower half of Victoria's body was almost certainly a rare manifestation of the virus.
The doctors explained that Victoria must have caught the infection for the first time during her pregnancy and it must have manifested itself in the strange rash. They said that there was a one in 100,000 chance that she could have passed the virus on to her son.
This had in turn caused him to develop meningoencephalitis - a swelling on the parts of the brain called the meninges and the cephalus.
It is thought that this swelling or the initial infection that damaged Lucas' brain and caused him to develop cerebral palsy. Cerebral palsy is caused by damage to the brain, which normally occurs before, during or soon after birth.
Lucas was put on a strong dose of acyclovir - the active compound in many over the counter cold sore remedies - to fight the infection.
And since then the little boy has made slow but steady progress. He has managed to hit his milestones although he didn't crawl until he was 18-months-old and he didn't learn to walk until he was three.
Victoria said: "He's never going to be like other kids his age but he's such a cheerful child and that's all that matters."
One charity that has made life much easier for Victoria is Brainwave, which specialises in helping children with disabilities and developmental delays.
"I don't know what I'd have done if I didn't access to them," she said.
"They are so supportive and helped make feel like I know I'm moving in the right direction with Lucas."