THIS Is What Your Expired Makeup Looks Like Up Close

Sad fact of the day: Most makeup products only last a few months before becoming unsanitary (and sometime stinky). And while we know how hard it can be to part ways with your favorite tube of mascara, holding on to it past the expiration date can be downright dangerous. But don't just take it from us: This week, Reddit user Semicolon_Expected shared her findings from a little DIY makeup science experiment — and they’re only slightly disturbing.

The user posted two separate Reddit threads to the Makeup Addiction subreddit of swabbed makeup. One was a 5-year-old mascara and a 1-year-old lipstick, and after three days in petri dishes with no incubation, the two swabs grew several large colonies of white and yellow-colored bacteria.

So what does that mean? In layman’s terms: “Bacteria grows in nutrient rich environments, and agar plates are a nutrient rich environment,” Semicolon_Expected wrote. “Each colony represents at least one bacterium that reproduced to form its own little family, so the plate shows an approximation of bacterial population on the old mascara.”

To the naked eye, it looks pretty gross. But as several commenters pointed out, the growth here could be far worse. (Especially because the user admitted to not using the mascara very often.) According to Dr. Shereene Idriss, MD, a derm at Union Square Laser Dermatology in NYC, bacteria growth in mascara is common because of your lashes. “The main purpose [of lashes] is to protect your eyes by trapping bacteria and pollutants that can get into them,” she says. “Therefore, when you apply mascara, you are basically picking up that bacteria and introducing it into the tube of product.”

A good rule of thumb? Toss out your mascara every four to six months, says Dr. Idriss. “In addition, I strongly urge you consider cleaning your brush — no matter how messy that may seem — on a regular basis."