Drawing on medieval medical encyclopaedias, early modern and Victorian advice books, as well as twentieth scientific advice to mothers, and linking them to present-day mothering discourse in the media, this article discusses cultural attitudes towards breast-milk and nursing mothers. The texts present a paradox in that while breast-milk is claimed as the best food for an infant, and mothers who choose not to nurse are vilified, it is simultaneously discussed as a potential poison and corrupting agent. I argue that the fear of breast-milk is a symptom of a cultural anxiety that periodically resurfaces, constructing the maternal body as threat to the infant, a threat that must be controlled and contained.