DayQuil is a medicine designed to help relieve many symptoms of a cold and flu. Made by Vicks, it is available in liquid and "LiquiCap" (capsule) form. DayQuil's night time counterpart is NyQuil, which contains an antihistamine. This antihistamine is a sedative, and may cause NyQuil users to develop a marked drowsiness. Because DayQuil lacks this antihistamine, it does not cause the drowsiness,