A device for delivering an agent into breast milk while breastfeeding. In one embodiment, the device includes a breast shield modified to engage a non-woven material which has been impregnated with a milk soluble active agent such as sodium dodecyl sulphate (SDS). A lactating animal, e.g. a woman, uses this agent-delivering breast shield during breastfeeding to administer prophylactic or therapeutic agents to a suckling infant. The inventions are particularly well suited to preventing transmission of HIV virus from mother to child. Alternatively, the agent-laden material could be used with a baby bottle nipple or pacifier.