We Tested Our Makeup Brushes for Bacteria, and the Results Were Shocking

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Yes, we're told time and time again that our makeup brushes and sponges are hotbeds for gunk and bacteria. Yes, we know it's best to toss them after a certain amount of time, no matter how diligently we clean them. Yes, as beauty editors, who know a ton of beauty hacks, we really should know better. But here's the thing about microscopic particles—it's really easy to adopt an "out of sight, out of mind" mentality. There are (literally) bigger things to worry about, right? We called on experts Dr. Emmett Johnson and Dr. Jennifer MacGregor to speak to the effects of dirty brushes. 

Meet the Expert

  • Dr. Emmett Johnson is a microbiologist and professor at Tulane School of Medicine.
  • Dr. Jennifer MacGregor is a board-certified dermatologist.

But in reality, ignoring the problem can wreak havoc on our skin—or worse, our health. So in the name of a self-imposed reality check, we thought it only made sense to finally give ourselves a visual of what's really hiding on those brushes. We nabbed some agar Petri dishes on Amazon, swabbed some of our most-used brushes and go-to foundation sponge, and 72 hours and one makeshift incubator later, we had our answer.

Keep scrolling to learn from experts exactly what happens if you don’t keep your favorite makeup brushes clean.

Can Bacteria Actually Grow on Makeup Brushes?

Makeup brushes with petri dish

ISABELLA BEHRAVAN

First off, it's worth noting that all of these brushes—save for the sponge and the brush you see above—had been cleaned just a couple of weeks before and hadn't been used since. We did this to illustrate the fact that even if you wash your brushes regularly, it's impossible to completely remove all contaminants, especially over time. These brushes are also stored in open jars, so some of the bacteria could be a result of open-air exposure.

an iPhone and a Petri dish
Isabella Behravan

We also tested an iPhone as a control plate—phones are notorious breeding grounds for bacteria, so we thought it could be useful as a comparison tool. Surprisingly, it seemed relatively clean—cleaner than a few of the brushes we tested, at the very least.

makeup brush and Petri dish
Isabella Behravan

For the experiment, we swabbed the brushes, sponge, and phone individually, and then spread the swab all over its designated plate. We then incubated the plates together for three days—and began to see bacteria colonies appear in a matter of hours. 

blush brush and petri dish
 ISABELLA BEHRAVAN

The fact that the bacteria only appeared in some spots on the plate is definitely noteworthy—if the brushes were extremely contaminated, the colonies would have grown throughout the plate's entire surface area, says Johnson. Still, the fact that bacteria appeared at all after the brushes had recently been cleaned is a little disheartening—and eye-opening.

makeup brush and Petri dish
Isabella Behravan

The newest brush we tested produced the least bacteria by far—offering evidence that even with regular cleaning, brushes simply accumulate more and more stubborn bacteria over time. It's for this reason that it's wise to replace your brushes after a few years.

makeup brush and Petri dish
Isabella Behravan

As for the types of bacteria we saw, Johnson identified the white colonies as bacterial, while the orange spots are a mix of streptomycete (another strain of bacteria) and fungus. "They're just different kinds of common surface contaminants," he says. 

makeup blending sponge and Petri dish
Isabella Behravan

We'd be lying if we said that we weren't most wary of our beauty sponge, since countless dermatologists and skin pros have warned us about their potential to be extremely unsanitary. But the results speak for themselves—this six-month-old sponge was not freshly cleaned, yet only one small fungal colony appeared. (Still gross, but a pleasant surprise nonetheless).

How to Properly Clean Your Brush

But not so fast—unless they smell, are several years old, or remain stubbornly dirty even after a thorough scrubbing (color stains notwithstanding), there's no need to toss your brushes just yet. The lesson here is more about how important it is to care for your brushes and to not overlook what you simply can't see.

MacGregor stresses the importance of cleaning your brushes. "It would be like rubbing a dirty washcloth or sponge on your skin, causing acne, infection, and irritation," she says of using dirty brushes.

Wash your brushes on a weekly basis, and ideally, store them in a drawer or case where they have limited exposure to air. In between cleaning, MacGregor recommends spraying alcohol or diluted vinegar on your brushes to disinfect after every use. Even with weekly cleaning, you should replace your brushes every few years.

Our Favorite Ways to Clean Brushes

Consider adopting some of these genius cleaning hacks and products that Byrdie editors swear by:

Miracle Bar
Joanna Vargas Miracle Bar $22
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"I love using a bar of soap so I can rub the brush or sponge right onto it," says senior editor Lindsey Metrus. Former features editor Amanda Montell also abides by this technique.

Johnson's baby shampoo
Johnson's Baby Shampoo $5
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Deven Hopp, Byrdie's former beauty director, swears by drugstore baby shampoo to cleanse her brushes.

brush cleaner
Mary Kay Brush Cleaner $10
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Senior editor Hallie Gould is a fan of Mary Kay's formula. "I spray it on paper towels and the brush, and then rub it until product totally comes out," she says.

Express Brush Cleaning Mat
Sigma Express Brush Cleaning Mat $29
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As for me, while I still have yet to find my holy grail cleansing formula, I'm a huge fan of Sigma's handy cleaning mat, which suctions onto your sink and has grooves for a thorough scrubbing. It also doubles as a drying rack once you're done cleansing.

This article was originally published Jul 29, 2016.

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