Makeup brushes are fantastic tools for flawless, sanitary makeup application... if you keep them clean. Here are some quick tips to make sure that your tools stay squeaky clean and bacteria-free:
One of the most important things you can do to keep your brushes clean is to use a daily brush cleanser. I use a Sephora Collection spray cleanser on my brushes every day or two. To use spray cleanser: Spritz your brush 2-3 times, then swirl it around on a paper towel until the brush is entirely clean. You'll know your brush is clean because it will stop leaving makeup streaks on your paper towel. When the brush is clean, use your fingers to gently reshape the bristles back to their original form. I like to spot clean at night so my brushes can dry overnight.
To clean lip brushes or brushes that you use with a gel-based product (like a gel liner or a very creamy foundation), rub a little olive oil into the bristles of the brush and follow the same procedure as above.
It's also important to deep-clean your brushes every few weeks. Don't deep-clean more than once a week, or else you'll dry out the bristles and your brushes won't last as long as they normally should. You can invest in a moderately expensive, professional quality brush shampoo and follow the directions on the bottle... or you can make your own brush cleanser with two products that you have in your kitchen already. It's your choice :)
To make your own brush shampoo, just mix 2 parts warm water with one part vinegar OR mix one part seltzer water with one part rubbing alcohol. In a bowl, place just the tips of the brushes into the mixture of your choice. (Do not submerge the brush in near the ferrule, the metal ring that attaches the bristles to the brush handle; if you get your brush wet too deep down, the bristles will never dry and your brush will be ruined.) Once your brush is wet, swirl it in circular motions (for a round topped or dome brush) or back-and-forth (for a flat-top or eye shader brush) on a sturdy paper towel until the brush no longer leaves a makeup trail. Let the brushes dry.
Be sure to never let your entire brush get wet.
Happy cleaning :)