It's common in over-the-counter cold and flu medicines, but it doesn't work. This is the ingredient the FDA plans to pull from store shelves.

Cold and flu season is upon us and Americans will be flocking to pharmacy shelves to pick up some medicine to alleviate their symptoms. But the ingredients list on many of these products might start to look very different based on new guidance from the Food and Drug Administration.

The U.S. Food and Drug Administration (FDA) is proposing to remove a common ingredient in nasal decongestants used by millions of Americans, citing data that shows it’s not effective. Oral phenylephrine is used in over-the-counter products like Sudafed and Dayquil to help temporarily relieve the common symptom of colds and allergies.

When you're feeling under the weather, you likely grab your go-to cough and cold medicine. But are all the ingredients helping you fight off that cold?

Phenylephrine is both the most common decongestant on pharmacy shelves, and arguably the worst at its job. Last year, the FDA's advisory panel ruled it should no longer be considered an effective drug.