Mucinex is an over-the-counter medication primarily used to relieve symptoms of cough and congestion caused by colds, flu, or allergies. Its active ingredient, guaifenesin, is an expectorant that helps thin and loosen mucus in the airways, making it easier to cough up and clear out. Mucinex is available in various forms, including tablets, liquids, and extended-release formulations. It is important to follow the dosage instructions on the packaging or as directed by a healthcare professional to ensure safe and effective use. Always consult a doctor if symptoms persist or worsen.