When your sinuses aren't working, it can lead to several situations. Most commonly aches and congestion. Pressure on sinus walls can be caused from air trapped within a blocked sinus. Liquids may add to this pressure, bringing along with it the intense pain of a sinus attack. In addition, if your membranes become swollen, they can prevent air from entering your sinuses, creating a painful vacuum effect. This is where Sudafed can help. Sudafed is a brand name and registered trademark for a family of over-the-counter (OTC) decongestants. The name is a reference to the active ingredient, pseudoephedrine hydrochloride, traditionally associated with the product, which is a type of medicine called a decongestant. So, with this added ingredient, Sudafed can combat the symptoms of your cold/flu almost immediately.