The difference between diphenhydramine hydrochloride and diphenhydramine citrate is that the salt used to bind the diphenhydramine, is different. For diphenhydramine hydrochloride the salt is hydrochloride and for diphenhydramine citrate the salt is citrate. This salt can change how quickly and effectively the diphenhydramine dissolves and is absorbed but once it is in the body it has no effect. Essentially 25 mg of diphenhydramine hydrochloride is equivalent to 38 mg of diphenhydramine citrate.