Sudafed is a popular over-the-counter medication used to treat nasal congestion caused by allergies or colds. There are a variety of synonyms for Sudafed, including pseudoephedrine, phenylephrine, nasal decongestants, and cold and flu relief. These synonyms contain similar active ingredients that target the symptoms of nasal congestion by constricting the blood vessels in the nasal passages, reducing inflammation and allowing air to flow more freely. It is important to consult a doctor or pharmacist before taking any medication to ensure it is safe and effective for individual use.