Nytol caramel 300ml is a clinically proven sleep aid that contains the active ingredient diphenhydramine hydrochloride, which is an antihistamine that works by blocking the body�s response to histamine � an agent that is responsible for causing an allergic response such as hay fever, stings and rashes. Histamine also looks after the brain-s waking system so diphenhydramine hydrochloride can help alleviate temporary sleeplessness.