The Food and Drug Administration on Thursday proposed removing a common ingredient in over-the-counter cold medicines that was found to have no effect on nasal congestion, despite its widespread use for decades.

The proposal stems from a recommendation issued just over a year ago by a panel of experts who agreed unanimously that the ingredient, called phenylephrine, did not work when taken in liquid or pill form. It is still considered to be effective in nasal sprays.

The ingredient has been used alone and in combination with other pain killers, cough suppressants and other agents meant to ease cold and flu symptoms in medications like Tylenol, Mucinex and Benadryl.

“It is the F.D.A.’s role to ensure that drugs are safe and effective,” said Patrizia Cavazzoni, the director of the F.D.A.’s drug division. “Based on our review of available data, and consistent with the advice of the advisory committee, we are taking this next step in the process to propose removing oral phenylephrine because it is not effective as a nasal decongestant.”

The agency emphasized that the ingredient was not considered unsafe.

The move brings the agency one step closer to getting products containing the ingredient pulled from store shelves. In issuing the proposal, the F.D.A. also began seeking public comments. The F.D.A. said it would give companies additional time to reformulate their products if the proposal was finalized.

Scott Melville, chief executive of the Consumer Healthcare Products Association, a trade group representing companies that make over-the-counter drugs, said that he was “disappointed” with the agency’s decision. He said that the F.D.A. had backed phenylephrine for years and should continue to do so given many years of studies, not just new data that showed the ingredient didn’t work.