The invention relates to a method which includes the following steps: mixing hydrophilic components, including water and an emulsifying saponin which is less than 1% of the emulsion regardless of the proportion of the oily phase； mixing lipophilic components, including the oily active substance, which can reach 40% of the emulsion； a first homogenization of the two preceding phases using a rotor/stator or ultrasonic mixer until a mean diameter of less than 6 μm of the oily droplets is obtained； and a second homogenization of the preceding mixture using a high-pressure homogenizer until a mean diameter of less than 0.4 μm of the oily droplets is obtained.
