(KIAH) — The Food and Drug Administration (FDA) said the leading decongestant used by millions of Americans doesn’t actually work.

An expert panel reviewed the effectiveness of phenylephrine, which is found in over-the-counter versions of Sudafed, Dayquil and other cold medicines. The FDA advisers said new studies show oral phenylephrine was no better than a placebo at relieving congestion.

“Modern studies, when well conducted, are not showing any improvement in congestion with phenylephrine,” said Dr. Mark Dykewicz, an allergy specialist at the Saint Louis University School of Medicine.

The group’s negative opinion opens the door for the FDA to pull phenylephrine from a federal list of decongestants deemed effective. There’s unlikely to be any immediate impact from Tuesday’s panel vote, which is not binding.

If the FDA follows through on the panel’s recommendations, Johnson & Johnson, Bayer and other drugmakers could be required to pull their oral medications containing phenylephrine from store shelves. That would likely force consumers to switch to the behind-the-counter pseudoephedrine products or to phenylephrine-based nasal sprays and drops.

In that scenario, the FDA would have to work with drugstores, pharmacists and other health providers to educate consumers about the remaining options for treating congestion, panelists said Tuesday.

The group also told the FDA that studying phenylephrine at higher doses was not an option because it can push blood pressure to potentially dangerous levels.

“I think there’s a safety issue there,” said Dr. Paul Pisaric of Archwell Health in Oklahoma. “I think this is a done deal as far as I’m concerned. It doesn’t work.”

The Associated Press contributed to this report.