Doxylamine is an antihistamine, used to relieve symptoms of allergy, hay fever, and the common cold. This medication works by blocking certain natural substances (histamine, acetylcholine) that your body makes. This effect helps to relieve allergy/cold symptoms such as watery eyes, runny nose, and sneezing.Cough-and-cold products have not been shown to be safe or effective in children younger than 6 years. Do not use this product to treat cold symptoms in children younger than 6 years unless specifically directed by the doctor. Also, do not give the 25 milligram tablets to children younger than 12 years, unless directed by the doctor. Ask your doctor or pharmacist for more details about using your product safely.These products do not cure or shorten the length of the common cold and may cause serious side effects. To decrease the risk for serious side effects, carefully follow all dosage directions. Do not use this product to make a child sleepy. Do not give other cough-and-cold medication that might contain the same or similar ingredients (see also Drug Interactions section). Ask the doctor or pharmacist about other ways to relieve cough and cold symptoms (such as drinking enough fluids, using a humidifier or saline nose drops/spray).