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Phenylephrine May Not Be Effective for Nasal Congestion

In many parts of the US, a new allergy season is beginning. Runny nose, watery eyes, and congestion are common symptoms of seasonal allergies. There are a variety of treatments offered, but it is not clear if they are effective. Phenylephrine and pseudoephedrine (eg, Sudafed) are two common drugs given to relieve nasal congestion.

ENT University in Vienna conducted a study to review the effects of these drugs on nasal congestion from seasonal allergies. Their study, published in the Annal of Allergy and Asthma Immunology , found that pseudophedrine may be effective, but phenylephrine was no different from placebo .

About the Study

The study was a small randomized crossover trial . In a crossover, each participant is eventually exposed to all of the options that were studied. The 39 participants were all sensitive to grass pollens. They were exposed to this pollen in a special chamber that can deliver measured amounts of pollen. After the exposure the participants were given one of the following:

  • Phenylephrine 12 mg
  • Pseudoephedrine 60 mg
  • Placebo

Over the following six hours, participants were monitored and asked to rate their nasal congestion. At the end of the trial participants reported:

  • Significantly better results with pseudophedrine compared to phenylephrine and placebo
  • The same results for phenylephrine compared to placebo

Neither medication relieved non-nasal allergy symptoms.

How Does This Affect You?

This was a small study. The larger the study, the more reliable the results will be. Despite this limitation, there is a suggestion here that products containing pseudoephedrine are more likely to effectively relieve your allergy symptoms than those containing phenylephrine. In addition to these over-the-counter medications, your doctor is able to prescribe other medications supported by more convincing evidence of effectiveness.

In general, to help manage seasonal allergies, try to avoid peak pollen times, such as 6am-10am. When doing activities that may stir up pollen (like cutting grass), wear a mask. Learn what times of year your allergies tend to occur and make a plan to begin preventative steps. If you suffer from severe seasonal allergies or have allergic symptoms all year round, you may wish to speak to your doctor about preventive treatments, such as allergy injections .




  • Speroff L, Gass M, Olivier S; Study 315 Investigators. A placebo-controlled study of the nasal decongestant effect of phenylephrine and pseudoephedrine in the Vienna Challenge Chamber. Ann Allergy Asthma Immunol . 2009 Feb;102(2):116-20.

Last reviewed April 2009 by Richard Glickman-Simon, MD

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