The Active Ingredient in Cold and Flu Tablets is Useless, Medical Professors Say

They say the active ingredient, phenylephrine, causes a placebo effect.

Boxes of over-the-counter cold medication in Milwaukie, Oregon in this file photo. Craig Mitchelldyer/Getty Images

Less than 1 percent of the active ingredient in cold and flu tablets enters the bloodstream, causing only a placebo effect, according to a medical professor.

University of New South Wales (NSW) Pharmacology Head Associate Professor Nicola Smith said the oral ingredient, phenylephrine, found in over-the-counter cough and cold medicine to relieve congestion temporarily, does not reach the nose.