You should be washing your brushes at least once a week.

According to celebrity makeup artist Allan Aponte , the brushes you use the mosti.e. usually your foundation and concealer brushesshould be cleaned once a week while everything else is usually fine to only be cleaned once or twice a month.

Brushes that you get wet or use liquid products with are also more important to keep clean because "moist environments allow for an overgrowth of bacteria and fungi," says dermatologist Joshua Zeichner, MD, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City. This is especially crucial if you have sensitive or acne-prone skin.

Only wash the tips of your bristles.

Rather than dunking your whole brush head into a bowl of water, Aponte suggests only getting the ends of your bristles wet under lukewarm, running water. "Submerging the whole brush head will eventually dissolve the glue that holds the brush together," explains Aponte.

Use a gentle, fragrance-free shampoo.

Aponte prefers baby shampoo over regular soap because it "still suds up and gets rid of dirt and oils but it won't dry out the bristles." His favorite one is the Aquaphor Baby Wash and Shampoo . In a bowl, pour a two to one ratio of water and shampoo. Dip the bristles into the mixture, then brush them from side to side in the palm of your hand until they lather up before rinsing under warm water. Continue this lather and rinsing cycle until the water running through your brush turns clear.

Do not use a blow dryer on your makeup brushes.

Once your brushes are clean, squeeze out the excess water with a paper towel then lay them flat onto a counter, with the bristles hanging over the edge to finish drying. "Never let your brushes dry upright as the water can go down the barrel that hold the bristles together and loosen the glue," explains Aponte.

You should replace your brushes at least once every year.

Maybe even more often if you use your brushes more frequently. Aponte says there are a few signs to look for, including if it's lost its shape, if the base of the brush head is shaking, if your bristles are constantly shedding, and if it's lost its fullness.