Robitussin Cough & Cold medicine contains the active ingredients guaifenesin, dextromethorphan and pseudoephedrine, according to WebMD. This combination treats cold, flu and allergy symptoms, such as cough, congestion and runny nose.
Specifically, guafenesin is an expectorant that thins and loosens mucus in the lungs, making it easier to cough up, according to WebMD. Dextromethorphan is a cough suppressant that reduces the urge to cough by acting on the cough center of the brain. Finally, pseudoephedrine is a decongestant that helps to alleviate runny nose and stuffiness. While none of these ingredients shortens the course of a cold, they can temporarily relieve symptoms.