Phenylephrine is a medication commonly used as a decongestant to relieve nasal congestion caused by colds, allergies, or sinus infections. It works by narrowing the blood vessels in the nasal passages, which reduces swelling and congestion, making it easier to breathe. Phenylephrine is often found in over-the-counter products, including tablets, liquids, and nasal sprays. In addition to its use as a decongestant, phenylephrine can also be used to increase blood pressure in certain medical situations, such as during surgery or in patients with low blood pressure. It is important to use phenylephrine as directed, as misuse can lead to side effects like increased heart rate or elevated blood pressure.