Phenylephrine is the most common active compound in over-the-counter drugs like Benadryl Allergy Plus Congestion, Sudafed PE, and Tylenol Cold and Flu Severe Day & Night.

But an FDA panel said after a two-day review that the oral decongestant 'is not effective' at standard or even high doses compared to a placebo.

Their ruling is not binding but strongly suggests the agency could soon heed their advice and pull its approval, forcing companies to pull or reformulate their products. 

The ingredient is protected under the FDA's Generally Recognized as Safe and Effective (GRASE) designation, but a reversal of its approval could mean manufacturers including Bayer and Johnson and Johnson might need to reformulate.

Phenylephrine is everywhere, so much so that nearly every nasal decongestant on pharmacy shelves contains it.

Drugs that contain it generated almost $1.8 billion in sales last year, according to data presented Monday by FDA officials. 

A unanimous vote by the 16-member Nonprescription Drug Advisory panel could issue a major blow to the industry.

Today's ruling only applies to oral formulations of phenylephrine.

If the agency decides to pull oral phenylephrine's GRASE designation, major manufacturers of drugs like Sudafed PE and Benadryl may be forced to reformulate them.

Phenylephrine was approved by the FDA in the 1970s to shrink the dilated blood vessels in the nose, relieving nasal and sinus congestion.