Diphenhydramine Citrate blocks the effects of the naturally occurring chemical histamine in the body. ?? Diphenhydramine Citrate is used to treat sneezing; runny nose; itching, watery eyes; hives; rashes; itching; and other symptoms of allergies and the common cold. ?? Diphenhydramine Citrate is also used to suppress coughs, to treat motion sickness, to induce sleep, and to treat mild forms of Par