There's a lot of buzz surrounding the new Lilumia Brush Cleanser, which InStyle called "a washing machine for your makeup brushes." The egg-shaped device holds six brushes and a small reservoir of soapy water. When you press a button, the machine rotates back and forth, delicately removing dirt and germs without damaging your brush's handle, hairs, or fibers. It's pretty cool, sure, but it made us wonder: Do we need to be that worried about the bacteria on our kabuki and foundation brushes? According to Manhattan dermatologist Julie Karen, MD, yes and no. On one hand, the risk of contracting a major infection from your bristles is very small. On the other, there's no denying that these brushes — which come into regular contact with your skin — harbor bacteria and debris. "If you have an underlying condition — such as eczema, or acne, or a break in the skin — and use a dirty or contaminated brush, you certainly expose yourself to the risk of infection or just aggravation," she says. Dr. Karen recommends washing your brushes twice monthly — unless you share them with other people (and you really shouldn't be sharing them with other people unless you're a makeup artist). In that case, clean them every time you use them. Moisture is another major contributor to the accumulation of bacteria, so if you use a brush to apply your cream eyeliner or lipstick, Dr. Karen advises also washing it after each use. "If you have an environment [with moisture], it's more likely that the bacteria will be harbored or reside there," she says. Which brings us back to the Lilumia Brush Cleanser: Is it truly worth your money ($149)? "To actually kill scores of bacteria, you need to achieve very, very high temperatures — like when you’re sterilizing instruments — and it's not coming anywhere close to that," says Dr. Karen. "You can probably get a just as good clean using warm, soapy water." So while we know it might be a little excessive, the same can be said of services that do your laundry, blow out your hair, or pick up your groceries. If you're a makeup artist or regularly use a variety of makeup brushes, you might consider this a good investment. If not, you can go back to your regularly scheduled brush cleaning.