Robitussin is a brand of cough medicine that is used to relieve coughs caused by the common cold, bronchitis, and other breathing illnesses. It contains a combination of active ingredients, including dextromethorphan and guaifenesin. Dextromethorphan is a cough suppressant that acts on a part of the brain to reduce the urge to cough, while guaifenesin is an expectorant that helps to thin and loosen mucus in the airways, clearing congestion and making breathing easier. Robitussin can also be used to temporarily treat cough, chest congestion, and stuffy nose symptoms caused by the common cold, flu, allergies, hay fever, or other breathing illnesses. It is available in both prescription and nonprescription products, and it is important to carefully follow all dosage directions to decrease the risk of serious side effects. It is also important to check the labels of all medications to make sure you are not taking more than one product containing guaifenesin or dextromethorphan.