Parents across the country are being warned not to give cough and cold medicines to children under six because of "limited evidence" they work and rare but real risks of potentially serious reactions.

Health Canada is ordering manufacturers to relabel over-the-counter cough and cold medicines to state "do not use in children under six," a move that will affect 722 products now authorized for sale in Canada.

The decision, which goes further than any country, follows a Health Canada review of the medicines and consultation with a panel of outside experts. The agency says reports of misuse, overdose and rare side effects "have raised concerns about the use of these medicines in children under six."

Between January 1995 and May 2008, Health Canada received 164 reports of adverse reactions in children under 12 related to cough and cold products; 105 were considered serious, including five deaths in children under the age of two. The youngest was four weeks old; the oldest, 20 months.

The reports are based on suspicion only and most of the children who died had serious underlying medical illnesses. But it's believed only about one per cent of adverse drug reactions are ever reported under Canada's voluntary reporting system.

Reported side effects in children using over-the-counter cough and cold products include convulsions, increased heart rate, decreased consciousness, abnormal heart rhythms and hallucinations.

The active ingredients affected by the decision include antihistamines in cough and cold medicines, dextromethorphan and other "antitussives" used to treat coughs, expectorants used to loosen mucus, and decongestants.

Drug makers last year pulled over-the-counter children's cough and cold products off Canadian store shelves amid fears the medicines could lead to an overdose and other potentially fatal reactions. At that time, Health Canada issued a warning to parents not to give cough and cold medicines to children under two, unless otherwise instructed to do so by a doctor.

According to Health Canada, the decision to expand that to kids under six is based on several factors: no evidence they benefit children; a higher number of reactions reported in the under six-year-olds (there are three times more reports of "serious adverse events" in younger children); younger children generally have more colds, and so are likely to get the medicines more often; they're less able to communicate when they experience potential side effects; and the products are used for symptoms that usually get better on their own.

There will be additional wording on the labels as well, such as not to use antihistamines to make a child sleepy. Child-resistant containers will become universal, and the products will come with accurate dosing devices.

The new decision does not apply to single-ingredient children's pain relievers and fever reducers.

"Cough and cold medicines have a long history of use in children, and reports of health problems related to the use of these products are very rare compared to their overall use," Health Canada spokesman Dr. Marc Berthiaume, director of the marketed pharmaceuticals and medical devices bureau, told reporters during a conference call Thursday.

"Parents can be reassured that there is no evidence that children who have used these medicines in the past are at risk of adverse events."

"We're not talking here about drugs that are dangerous, except in specific circumstances," Berthiaume added in an interview. "These drugs have been used for millions of doses for a number of years" and most of the rare side effects are related to accidental ingestion or misdosing, he says. Some parents may misread labels and give too much medicine to their children.

The labelling update will be completed by next fall, in time for the 2009 cough and cold season. Products with the old labels will remain on the market. Health Canada says they can still be used in children aged six and older.

Industry spokesman Gerry Harrington says that, when used as directed, children's cough and cold medicines have an excellent safety record, and that effectiveness studies in children are underway.

Dr. Michael Rieder, a spokesman for the Canadian Paediatric Society, called the move to restrict cough and cold medicines in younger children "a sensible decision."

"Deaths are rare, but they occur, so any death is a problem," says Rieder, researcher with the Children's Health Research Institute at the University of Western Ontario in London.

"Our message to parents is that we don't believe these products work in children under six, there may be potential safety issues, so you should use a fallback. A little bit of fever control, a lot of fluids and a bit of time will make you better just as quickly as anything else."

"Basically it's kind of waiting it out," Rieder says. "I know people don't want to hear that, because we live in an age in which immediate gratification is kind of a cultural thing."

Effective advertising also makes parents think the products work in younger children, he says. "There's the idea that they work. And many adults take a cough and cold medicine and it actually makes them feel better, so they think, if it makes me feel better, it should make my child feel better. But children aren't small adults."

Health Canada says children should not be given any medications labelled only for adults. If cough or cold symptoms worsen, last for more than a week or are accompanied by a fever higher than 38 C, or children are producing thick phlegm, parents should consult a health care practitioner.

For more information about Health Canada's decision on the use of cough and cold medicines in children, people can call toll free at 1-866-558-2946 or consult Health Canada's website at http://www.hc-sc.gc.ca.