An article published this week in Business of Fashion tracks the recent trend in Japan of buying secondhand luxury beauty products, which gives young people a chance to own coveted beauty staples that may be outside of their price range. Japan’s secondhand beauty market can be explained by Japan’s thriving secondhand retail sector as well as a cultural emphasis on avoiding waste (referred to as mottainai, which is often translated as “what a waste”).

“When I buy secondhand cosmetics, I always carefully look thorough about how many times has [it] been used and expiration dates,” Marika Sakamoto, a 28-year-old Tokyo dweller who has purchased used RMS Beauty and Nu Skin products on Mercari, tells BoF. “Mercari helps [make] buying these products easier, because you can’t buy them in Japan and people really don’t mind if they’re used,” she continued.

Another Mercari user, who has sold makeup on the site, tells BoF, “I was so surprised that most of [my listings] were sold within a few days,” says Tokyo-based Moe Miura, who has sold used Chanel, YSL Beauty, and Clinique products. She predicts that secondhand beauty will continue to gain traction.

But the used beauty trend isn’t unique to Japan, BoF reports. “On West Coast–based Glambot in the US, shoppers can find Giorgio Armani’s Chinese New Year highlighter palette with ‘80 percent fill’ remaining for $44.50 instead of the original $89. Peer-to-peer shopping app Depop, Lithuanian Vinted, and Reddit also provide platforms and forums for users to buy used cosmetics,” they write.

However, consumers may want to think again before dipping into the used makeup market. Dr. Joshua Zeichner, the director of cosmetic and clinical research at the Mount Sinai Hospital in New York, explains to Teen Vogue why he does not recommend using secondhand makeup. “Unlike secondhand clothing, used makeup is a bad idea. When you purchase makeup new from the store, you know it is not contaminated and fresh from the manufacturer. When you buy a product that was previously used, you have no idea what it may have come in contact with before getting to you,” he tells Teen Vogue. Consumers should be especially skeptical around secondhand liquid foundations, primers, lipsticks, glosses, and eye products, which Dr. Zeichner explains are particularly susceptible to contamination from microorganisms. “Never buy a product that directly touches the skin,” he says. Consider us amply warned!

“Even if you throw away the applicator, if it previously was stepped into the product the whole makeup may be contaminated. You have no way of knowing if the previous user had any skin infections like impetigo or cold sores,” Dr. Zeichner says. He also reminds us that we shouldn’t be using testers at a makeup store (remember: Stores like Sephora have generous return policies that let you return products after a certain amount of time that aren’t working for you!). “Even with the habitual ‘swatching’ and testing of shades and formulas in the most high-end department stores, sharing makeup is extremely unhygienic,” writes BoF.

Dr. Zeichner’s advice? “My best advice is to buy your designer clothing from a consignment store so you can save enough to purchase new makeup.” Okay! We will.