An over-the-counter pharmaceutical icon just took a hit. Last month, the Food and Drug Administration’s Nonprescription Drugs Advisory Committee discussed the efficacy of phenylephrine, the nation’s most popular oral nasal decongestant. Used for the temporary relief of stuffy nose, sinus, and ear symptoms caused by the common cold, flu, and allergies, it is the active ingredient in products such as Sudafed PE and some versions of Mucinex, DayQuil, Tylenol sinus, and Advil sinus congestion, as well as store brands based on the same formulations.