regular hand washing reduces the spread of cold viruses. it is most effective and is especially recommended for use in children, due to a lack of evidence supporting the effectiveness of over-the-counter cold medicines for children, and due to the risk for harm from those medicines. in 2009, canada restricted the use of over-the-counter cough and cold medication in children six years old and younger due to concerns regarding risks and unproven benefits. the misuse of dextromethorphan (an over-the-counter cough medicine) has led to its ban in a number of countries.