It's so important to clean your make-up brushes as often as possible! All your dead skin, old make-up and bacteria have gathered on this brush! Hence, if you are using a dirty make-up brush after cleansing, exfoliating and preparing your skin before you put your make-up on , you are just putting all the dirt you took off your skin back on it! This can cause extreme break-out. To wash your brushes wash them exactly how you wash your hair. Keep shampooing under the tap until the colour completely runs out of the brush and the running water stays clear. Then condition it, wash the product out and place the brush on a towel to dry over night. By the morning your brush should be clean and dry, ready to use! I do this routine about once a month not so much with my eye-shadow brushes but especially with my foundation, blush and contouring brushes because I use them regularly.