Phenylephrine is a key ingredient found in many over-the-counter cold and allergy medications across the country, including Sudafed PE, Vicks Nyquil Sinex Nighttime Sinus Relief and Benadryl Allergy Plus Congestion. On Tuesday, a Food and Drug Administration advisory panel determined that phenylephrine is ineffective in products used orally, potentially disrupting a $1.7 billion-per-year industry.

The FDA re-evaluated the initial findings used to support the use of the ingredient in decongestants, which first gained popularity in the early 2000s. Those findings are now believed to be “unsound.”

“In conclusion, we do believe that the original studies were methodologically unsound and do not match today’s standard,” Dr. Peter Starke, an FDA official who led the review of phenylephrine, told NBC News. “By contrast, we believe the new data are credible and do not provide evidence that oral phenylephrine is effective as a nasal decongestant.”

In 2022, American consumers spent over $1.7 billion on over-the-counter oral decongestants that contained phenylephrine (PE).

“We are aware that a number of excellent treatments are available for the treatment of nasal congestion, and in particular, congestion associated with allergic rhinitis,” according to the study. “That stated, as may be seen from the use data above, a significant amount of money is spent by consumers every year on the purchase of products that contain at least one ingredient (oral PE) that may not be effective. In addition to avoiding unnecessary costs of taking a drug with no benefit and lowering of overall healthcare costs, other potential benefits might be derived by changing the GRASE status of oral PE.

“These include but are not limited to avoiding any delay in care due to taking a drug that has no benefit, avoiding the risks of potential allergic reactions or other side effects related to use of PE in combination products, avoiding the inherent risks (especially for combination therapies) of taking more in order to seek some benefit, avoiding the risks of medication use in children, and avoiding missed opportunities for use of more effective treatments (including seeing a doctor if needed).”

If the FDA decides to revoke the drug’s over-the-counter designation, products containing the drug may need to be removed from shelves entirely.