Pseudoephedrine 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. Pseudoephedrine is often found in over-the-counter cold and allergy medications. While effective, pseudoephedrine can have side effects, including increased heart rate, insomnia, and dizziness. Due to its potential for misuse in the production of methamphetamine, many countries regulate its sale, requiring consumers to show identification and limit the quantity purchased. Always consult a healthcare professional before using this medication.