What can I take to treat a cough while also taking benadryl (diphenhydramine)?

Need diagnosis... First, your cough needs to be diagnosed by your doctor. Possible etiologies include acute bronchitis due to bacterial or viral infection, bronchospasm from any cause, gerd, sinus problems or even a combination of these. Chronic bronchitis, a form of copd, is a possibility especially if you have smoked. Treatment depends on diagnosis so see your doctor so this cough can be diagnosed!