By Jane Elliott
BBC News health reporter
Most parents will agree that nurseries are breeding grounds for coughs, colds, and tummy upsets.
Parents feel children often more ill after starting nursery
When a young child starts at nursery, they seem to suffer an endless cycle of minor ailments, that then seem to infect the whole family.
But the jury is still out about whether this is a bad thing, or whether early exposure to germs plays a key role in the development of a child's immune system.
Little research has been done in the UK into how many respiratory infections are caught by children attending nursery - and the knock-on efects this can have on the rest of the family.
Dr Nicol Black, a public health expert in Newcastle, has examined the issue in close detail.
He has just completed an 18-month study to examine whether there is any truth in the anecdotal belief that nursery attendance is linked to a greater risk of infection - and whether there are good grounds for promoting vaccination against certain illnesses.
Dr Black collated data from around 100 local nurseries and involving 550 episodes of illness.
His findings seem to support his contention that nurseries are a "wonderful melting pot" for infections.
"Pre-school children in day-care are three to four times more likely to have a respiratory infection than a child who stays at home," said Dr Black.
"And that fits what, anecdotally, parents are well aware of."
He added that in half the households studied, when a child became sick, others in the house were also ill either just before or just after the child.
About 13% of the adults were quite ill and had to have an average of six days off work.
Dr Black is to analyse the data further to assess further not only the health impact, but the economic impact on families, and the wider population in general.
He will look at issues such as whether illness spreads to other members of the household, and how much time off parents need to care for a sick child.
He will also look at whether prevention measures, such as vaccinations against serious conditions such as pneumococcal infection and flu, are needed.
The completed data from the study, which is expected to be published early next year, will be sent to the Department of Health.
But should we keep our children away from nurseries until they are older, or would that just be delaying the inevitable?
Research from the US has shown that children who attend nursery may be less likely to develop childhood leukaemia and that delaying their exposure to infection may result in them having an underdeveloped immune system, which puts them at a greater risk.
Dr Jackie Bucknall, consultant paediatrician at the Homerton Hospital, in London, believes there is no good health ground for not sending children to nursery.
"If you have a child that is fit and well and has not got any condition that can make them immunosuppressed, such as receiving cancer treatment, then I would recommend all parents to send their children to a place where they have got a good peer group mix.
"Although it may often seem that they always have a runny nose this is the way they stimulate their immune system.
"There is no problem. Children are going to be exposed to infections at sometime and it is probably better that it happens when they are nursery than when they are older."
Dr Bucknall stressed that toddlers were no more vulnerable to infection than those at school.
But she said it was important that children going to nursery were vaccinated against the most important childhood illnesses, such as measles, to protect themselves and others.
Mother Sam Salter, whose three-year-old Daisy goes to a local nursery agrees, saying she would rather Daisy had early exposure to infection.
"I would rather she had them now than when she went to school. It is easier for them when they are young and it is usually less serious.
"But I have noticed that Sean, my partner, has become more ill. He has had a lot more colds since Daisy started nursery."
Sam, from Surrey, has not had Daisy vaccinated against any illness, but says she does not worry about her becoming exposed to them.
She was not vaccinated herself as a child and had most of the illnesses including measles, German measles and whooping cough.
"I do not worry about her coming into contact with any of these childhood illnesses.
"But when we lived in London I was concerned about Daisy being exposed to TB and when there was an outbreak I would not go on the bus."