Dirt and bacteria accumulate on makeup brushes, which can cause breakouts. Wash foundation brushes once a week, and all your other powder brushes every 2-3 weeks. To wash them, simply use your facial cleanser or shampoo, or just classic soap that you mix with lukewarm water. Soak the brush in the mixture, but try not to get water above the handle of the brush because it could damage the glue that keeps all the bristles together. Rinse, pat dry, and lay it flat for drying.