This medication relieves cold and flu symptoms through several active ingredients. Phenylephrine helps to narrow small blood vessels, relieving nasal congestion and stuffiness. Diphenhydramine alleviates allergy symptoms, such as watery eyes, sneezing, and a runny nose. Paracetamol works by inhibiting the release of certain chemical messengers that cause pain and fever. Finally, caffeine enhances the effectiveness of paracetamol and reduces the drowsiness often caused by diphenhydramine.