The present invention relates to a process for producing an allergen extract from a biological allergen source material comprising the steps ofa) contacting the source material with a liquid extraction agent to produce a allergen extract mixture containing allergens dissolved in a liquid phase and a solid phase consisting of source material residues,b) subjecting the allergen extract mixture to a first separation step to remove the solid phase to produce a crude allergen extract,c) subjecting the crude allergen extract to a low molecular fraction removal step to remove molecules having a molecular size of less than 10 kDa, andd) carrying out step c) until the allergen extract has conductivity of below 2000 µS/cm at 25 °C to obtain a purified allergen extract.
