Chlorphen-12 relieves red, itchy, watery eyes; sneezing; itchy nose or throat; and runny nose caused by allergies, hay fever, and the common cold. Chlorphen-12 helps control the symptoms of cold or allergies but will not treat the cause of the symptoms or speed recovery. The active ingredient in Chlorphen-12 (chlorpheniramine maleate) is in a class of medications called antihistamines. It works by blocking the action of histamine, a substance in the body that causes allergic symptoms. Chlorphen-12 is the only chlorpheniramine maleate that lasts 12 hours.