A process for purifying lactoferrin from milk the process comprises subjecting the milk to filtration with a filter of molecular weight cut off (MWCO) 30-50 kD to separate the milk into a retentate fraction comprising lactoferrin and a permeate fraction comprising growth factors and/or RNAses with a molecular weight of less than 30 kD. During filtration with the filter of MWCO 30-50 kD, the milk or retentate is subjected to salt treatment such that growth factors and/or RNAses flow into the permeate, the salt treatment comprising maintaining the milk or retentate fraction at a salt concentration of at least 0.2M NaCl or equivalent or a conductivity of at least 20 mS/cm during the filtration with the filter of MWCO 30-50 kD.
