A decongestant is a type of medication that helps 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 allows for easier breathing. Common forms of decongestants include nasal sprays and oral tablets. Decongestants can be found in many over-the-counter products, often combined with other medications like antihistamines or pain relievers. While effective, they should be used as directed, as overuse can lead to rebound congestion or other side effects. Always consult a healthcare professional if unsure about their use.