Jasper Allen, two, spent five days in hospital after his chicken pox became severely infected.
His mother, Sarah Allen, 36, who is a nursery manager, said they were refused a GP appointment less than 48 hours before he was rushed to hospital.
Jasper is now recovering and joined the show’s hosts Eamonn and Ruth in the studio, who asked Dr Chris
Dr Chris said: “Sarah has seen it all.
"Basically we view chicken pox as very common, very contagious and a mild disease children get and get away from. Seeing his pictures there and his temperature getting so high and getting worse by the day, they are they alarm bells.”
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Sarah said at first she had no concerns about her son.
“My daughter had it," she said. "We just thought he would get some spots and be grouchy.
“Every single day he had more and more and more arriving. He had them on top of each other.
“I phoned the GP up to say he has got quite bad chicken pox. They said they wouldn’t see him.”
But Sarah said it wasn’t until the next say when his temperature was hitting 40 degrees and he wasn’t eating or drinking that she needed to take drastic action.
“I thought he had a really bad case of chicken pox.
“Luckily an amazing nurse was walking out and he said he needs to be admitted and needs to be admitted now.”
However, it has since emerged that Jasper’s sister had chicken pox a week or two before hand.
Dr Chris added: ”Also he had scarlet fever developing the week before. His immune system was trying to fight that.”
Sarah is now calling on the government to make the chickenpox vaccination part of the NHS's routine childhood immunisation schedule so it is automatically available for all children.
It is currently available privately - but parents have to pay and it is usually only offered to protect people at risk from serious illness - such as those with weakened immune systems.
Sarah said her children have had all their immunisations but she said it never crossed her mind to get them vaccinated privately.
But she said she would have liked the choice.
Dr Chris said the government will be making a decision next year as to whether it routinely vaccinates all children.
But he said chicken pox is usually a mild illness in children, adding they do ‘bounce back very quickly’.
He added: “When you look at the Department of Health - the cost of vaccinating every single child against the disease is a lot, and the illness not as serious as measles, mumps.”
Ruth asked Dr Chris what advice he would give to parents.
“If the temperature soars, if they get more ill, if you are concerned ring your GP and go from there. One in ten thousand children do get a reaction."