Washington ? The medicines long used by parents to treat their children’s coughs and colds don’t work and shouldn’t be used in those younger than 6, federal health advisers recommended Friday.

The over-the-counter medicines should be studied further, even after decades in which children have received billions of doses a year, the outside experts told the Food and Drug Administration. The FDA isn’t required to follow the advice of its panels of outside experts but does so most of the time.

“The data that we have now is they don’t seem to work,” said Sean Hennessy, a University of Pennsylvania epidemiologist, one of the FDA experts gathered to examine the medicines sold to treat common cold symptoms.

The recommendation applies to medicines containing one or more of the following ingredients: decongestants, antihistamines and antitussives. It doesn’t apply to expectorants, though many of the medicines also contain that ingredient.

The nonbinding recommendation is likely to lead to a shake up in how the medicines – which have long escaped much scrutiny – are labeled, marketed and used. Just how and how quickly wasn’t immediately clear.

“If the agency chose to restrict use in children 6 and under, that won’t necessarily lead to a ban on the products. It might lead to labeling that says ‘do not use,”‘ said Dr. John Jenkins, director of the FDA’s office of new drugs.

Such labeling changes could take years to put in place, since the FDA would have to undertake a lengthy rule-making process. Jenkins suggested if the drug industry took it upon itself to make such changes, the FDA could use its enforcement discretion to allow it to do so more quickly than would be done otherwise.

In fact, the Thursday-Friday meeting came just a week after the industry pre-emptively moved to eliminate sales of the nonprescription drugs targeted at children under 2.

So what are parents to do if they choose to use the medicines, pending further action? Jenkins recommended they follow the directions when giving the medicines to their children, and use them only as directed. He also counseled they pay close attention to what ingredients the medicines contain and to ask a doctor if they have any questions.

In two separate votes Friday, the panelists said the medicines shouldn’t be used in children younger than 2 or in those younger than 6. A third vote, to recommend against use in children 6 to 11, failed.

Earlier, the panelists voted unanimously to recommend the medicines be studied in children to determine whether they work.

That recommendation also would require the FDA to undertake a rule-making process to reclassify the medicines, since the ingredients they include are now generally recognized as safe and effective, which doesn’t require testing. Again, that process could take years, even before any studies themselves get under way.