Benadryl Cough Formula Syrup belongs to a class of medications called ‘expectorants’ used to treat cough. Coughing (dry or productive) is the body’s way of clearing irritants (like allergens, mucus, or smoke) from airways and preventing infection. There are two types of coughs, namely: Dry cough and chesty cough. A dry cough is tickly and doesn't produce any vicious or thick mucus, while a chesty cough (wet cough) means mucous or sputum is produced to help clear your airways.