When you’re shopping for the perfect serum to add to your skin-care regimen, things like five-star product reviews and a good-looking price tag can outshine where, exactly, you’re purchasing it from. Add to cart with the wrong retailer, though, and you could wind up with a bad reaction on your skin (or worse). That’s because in the world of counterfeit beauty products, buying fakes can pose a lot more problems than a knock-off designer bag would.

In a recent episode of Netflix’s docu-series Broken, industry insiders take a deep dive into the world of counterfeit beauty products, schooling viewers on just how prevalent—and problematic—the industry is. Seizures of counterfeit cosmetics have exploded—according to a recent report by the Organization for Economic Cooperation and Development, counterfeit goods value more than half a trillion dollars in the global economy, and US Customs and Border Protection figures say that counterfeit products cost over $75 million per year to the cosmetics industry. Thanks to the Internet, it’s easier than ever for people to sell knockoff cosmetics and pass them off as the real thing. For consumers, the consequences of this can either result in a non-effective beauty product… or you could face problems with your skin (like rashes).

“Counterfeit beauty products [can] include ingredients that have no business in skin care, like super glue for example, and they are often created in completely unsanitary makeshift labs. So, you might find vile contents mixed into the products you are placing on your face, which [can] include urine and fecal matter,” says board-certified dermatologist Whitney Bowe, MD, who appears in the film. “They have also tested positive for heavy metals like mercury and lead, known carcinogens like arsenic, and high levels of bacteria—some of which are known human pathogens.”

Super glue, for instance, was being used in counterfeits match the consistency of Kylie Jenner’s all-famous Lip Kit products… which would glue your lips together when you’re just trying to put on lip gloss. According to Dr. Bowe, in the worst case scenarios, using non-skin-care ingredients on your face can result in all sorts of unpleasant reactions, including rashes, chemical burns, and, well, your lips becoming physically glued together, like in the case we mentioned. As the counterfeit market becomes more and more prominent (thanks in large part, the film says, to influencers, the FOMO culture surrounding makeup launches, and the vast landscape of Internet commerce), it’s more important than ever to be sure that what you’re buying is the real deal. To help, Dr. Bowe lays out the best ways to spot counterfeit cosmetics.

How to spot counterfeit beauty products

1. Buy from a reputable seller: When you purchase products directly from a brand or an authorized retailer (like Sephora, Dermstore, Ulta, etc.), you know what you’re getting. Elsewhere on the Internet, it’s not so clear. Websites that work with third parties—which many, many people turn to for their beauty products—are hotbeds for fakes, and if you think you’re getting a great deal on something that’s usually super expensive or sold out elsewhere, chances are it’s probably too good to be true. And if you’re coming across a sought-after palette by way of a street vendor, you’re going to want to steer clear.

2. Check the reviews: If you are going to buy skin care on Amazon, for example, which has many third-party sellers, it’s important to research by reading a seller’s reviews. “If a seller has repeated negative reviews, or reviews that your gut tells you are ‘staged’ or ‘fake’ because they all contain nearly the exact same language, do not purchase your product from that seller—even if the price is so compelling and attractive,” says Dr. Bowe. “One way to stay in the safe lane is to purchase products that are sold and shipped by Amazon.com, rather than by third parties.” She also suggests consulting sites like Reviewmeta and Fakespot, which can help you identify fake reviews.

3. Don’t trust the packaging: Back in the day, you could spot a counterfeit based solely on shoddy packaging. Now, that’s a lot harder to do. “When I first started looking into counterfeit products years ago, there were some obvious red flags—print would easily rub off, packaging looked haphazard, safety seals were missing,” says Dr. Bowe. “Now, the packaging can look almost identical.” In other words, just because something looks legit doesn’t mean that it actually is, so it’s important to test the actual product or check out the retailer before slathering it all over your face.

4. Spot test: Testing new products on your arm or hand is always important, but it’s especially important in the case of counterfeits. If a product you’ve been using forever is suddenly giving you contact dermatitis when you try it on your wrist, it’s a good sign that it’s fake.

Instead of buying new makeup, hold onto the summer foundation shade you’ve got with these easy winterizing updates. And here’s exactly how often you need to wash your hair based on your texture.