WASHINGTON — Cold and cough medicines don’t work in children and shouldn’t be used in those younger than 6, federal health advisers recommended today.

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,” one of the FDA experts gathered to examine the medicines sold to treat common cold symptoms, Sean Hennessy, said. The recommendation applies to medicines containing one or more of the following ingredients: decongestants, expectorants, antihistamines, and antitussives.

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.

In two separate votes, 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 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. The process could take years, even before any studies themselves get under way.

Simply relabeling the medicines to state they shouldn’t be used in some age groups could be accomplished more quickly, FDA officials said.