Adjunctive haemostatic agents have been used in surgery for over 70 years. What surgeons may not know is that products intended for similar applications may have very different biological properties and that occasionally product upgrades may introduce a change in the material’s behaviour. Many of the agents employed to assist in haemostasis may have a biological (animal) origin. A recent case brought to light the need to recognise the possibility of biological interactions. As consideration into this surgical problem unfolded, religious and legal questions began to arise.