Brushes should be washed at least once a month to prevent a build-up of bacteria. If you don’t have a dedicated brush cleaner, gentle household products mixed with water works just as well. Rinse the brush under water (avoiding the barrel below the bristles) and swish gently in a bowl of unscented baby soap, shampoo or mild bar soap mixed with lukewarm water. Rinse again to remove the soap and lay flat on a clean try towel to dry.