You would not expect that this could be the reason for your winter cold.

Sick woman with cold

If you’re health-savvy, you already wipe down your cellphone, computer keyboard and gym equipment to avoid the spread of germs—but have you tackled your beauty bag? According to the U.S. Centers for Disease Control and Prevention, the average adult gets two to three colds every year. Good old soap-and-water hand-washing is the best defense against catching a bug, but what you put on your skin elsewhere matters too.

Your powder blushes, bronzers and foundations are less susceptible to contamination, even during flu season. New York City– and L.A.–based professional makeup artist Tomy Rivero says, “If you have not used a powder product in a while, just take a tissue and clean off the top layer of the product and it should be good to go.” However, you need to make sure you are cleaning your brushes and applicators at least biweekly. Rivero advises: “Use your hair shampoo (make sure there is no tint) to clean off your brushes and lay them out to dry overnight. This prevents bacteria from growing and allows for a cleaner application with your makeup, pulling the true colors in your cosmetics.” Some applicators, like the sponge BeautyBlender Original + Solid Cleanser Kit ($40, beautyblender.com), come with their own solution. Just remember to remove all the product when cleansing.

Rivero’s final advice is this: “Don’t leave your brushes and powders inside of the bathroom. The room moistens when you shower, and humidity is bacteria’s best friend. This will keep everything cleaner.”

Related: The Doctor’s Orders For Working Out Sick