Nyquil: temporarily relieves cold flu symptoms: nasal congestion, sinus congestion & pressure, cough due to minor throat & bronchial irritation, cough to help you sleep, minor aches & pains, headache, fever, sore throat, runny nose & sneezing. Reduces swelling of nasal passages. Temporarily restores freer breathing through the nose. Promotes nasal and or sinus drainage. Dayquil: temporarily relieves common cold/flu symptoms: nasal congestion, sinus congestion & pressure, cough due to minor throat & bronchial irritation, minor aches & pains, headache, fever, sore throat. Reduces swelling of nasal passages. Temporarily restores freer breathing through the nose. Promotes nasal and or sinus drainage. Helps loosen phlegm (mucus) and thin bronchial secretions to rid the bronchial passageways of bothersome mucus and make coughs more productive. Max strength. Dayquil: non-drowsy.