Neonates are given many medicines. A significant proportion of these medicines contain excipients. Excipients are used to facilitate the manufacture and use of medicines. Without excipients, it would not be feasible to formulate some drugs into appropriate medicinal products. For others the removal of excipients would reduce the shelf life and make them uneconomic to produce or too expensive for users to purchase. Excipients are also important because some of them can cause harm. Accordingly, it is important to minimize excipient exposure when possible and to only use them when there is a clear pharmaceutical requirement. On balance it is generally safe to use medicines containing excipients. This review introduces physicians and nurses to the functions of excipients in medicines and describes some potential adverse effects of excipients in neonates. The review also provides pharmaceutical scientists with an insight to issues that arise when excipients are administered to neonates. The review answers some key questions about excipients, addresses some case studies of excipient use, proposes approaches for clinicians who prescribe and administer medicines containing excipients and identifies areas for research that seeks to establish the safety profiles of excipients in neonates."