Everyday with mild soap and warm water. or you could use a brush cleaner. You should clean it everyday because of the product you use it with. If you ever use a brush to apply lipstick/gloss, cream eyeshadow/liner, or foudation, it should be washed every day to prevent the growth of bacteria and mold/mildew in the brush. Also, make sure you wash it with warm water, not hot, because if the water is too hot, it mght loosen and met the glue that hold the bristles into the brush, causing it to shed.
answered 5 years, 10 months ago