Good, quality makeup brushes are an investment. If you take care of them, they will take care of you. Cleaning, disinfecting, and conditioning your makeup brushes are essential – not only so that the brushes continue to work great, but also to help prevent spreading acne-causing bacteria and oil onto your face and into your makeup. Using dirty brushes are the equivalent of not washing your face.
Gently wash your brushes with luke-warm water and a little soap (I highly recommend using anti-bacterial liquid soap to sanitize them) mixed with extra virgin olive oil (this helps to condition the bristles and prevent them from drying out from the soap) once a week, or as needed.
The easiest way to do this is put the soap and olive oil together on a glass plate. Next, swish the brush around the plate (you will see all of the makeup breaking down) and then into the palm of your hand. Set aside and repeat on all dirty brushes. Gently rinse only the brush tops with luke-warm water under the faucet until the water runs clear. Using your fingers, gently squeeze any excess water off the brush as you reform the brush bristles. Lay flat overnight to dry. Cooling racks for baking work great for drying as it allows air to flow threw the bristles. Allow the makeup brush to dry fully before applying makeup to your skin.
If you take care of your brushes, they will last for years and will rarely need replacing.