The invention provides process for purifying RNAses and growth factors from milk or lactoferrin, the process comprising subjecting the milk or lactoferrin to filtration to separate it into a retentate fraction comprising lactoferrin and a permeate fraction comprising growth factors and/or RNAses, wherein prior to and/or during filtration the milk or lactoferrin is subjected to salt treatment such that growth factors and/or RNAses flow into the permeate. The invention also provides RNAses and growth factors obtained from the process of the invention.
