Phenylephrine is used to treat stuffy noses and sinus and ear problems caused by the common cold, allergies or the flu, according to WebMD. The medication decreases swelling in the nose and ears.
Phenylephrine HCL is the active ingredient in medicines such as Sudafed PE. Phenylephrine is a widely used alternative to pseudoephedrine, which is also a decongestant. Pseudoephedrine is more effective than phenylephrine but is also a key ingredient in making methamphetamine, explains Riverside Health System. Federal law requires non-prescription medicines containing pseudoephedrine to be kept behind the counter at pharmacies. Drug companies responded to this by replacing pseudoephedrine with phenylephrine in cold medicines, allowing consumers easier access to them.