Nyquil contains alcohol as an ingredient. Along with alcohol, it contains acetaminophen, dextromethorphan, and doxylamine succinate. Acetaminophen, dextromethorphan, and doxylamine succinate are the three main active ingredients. Acetominophen is used to reduce fever and pain, and is a common ingredient in many pain/headache medications. Dextromethorphan is a common cough suppresant. Doxylamine succinate is an antihistamine.