Skin care can be expensive, so of course we're always looking for ways to use every last drop of whatever serum, cleanser, or cream we slather on our faces. The internet is the first stop for lots of folks who are looking for ways to get the most mileage out of their pricey skin care. But not all methods are created equal. Some actually come at the cost of contaminating the products you were trying to preserve in the first place.

One of the latest product-salvaging hacks comes from thrifty Redditors, who are cutting in half the tubes that are housing their skin-care products to get to the excess goodness trapped inside. While it sounds like a genius way to be sure you're getting the most for your money, it's also a great way to absolutely eff up your product, and possibly your skin, according to the experts.

“By cutting tubes of beauty products, you are increasing the speed of oxidation and potentially exposing the spread of bacteria and fungus," says Melissa Kanchanapoomi Levin, a dermatologist and founder of Entiere Dermatology in New York City.

Products packaged in tubes rather than jars are more susceptible to contamination in the first place. According to Charleston-based dermatologist Marguerite Germain, this is especially important to remember with products made for around the eyes and mouth. (Germain does concede that hair, body, and rinse-off products are less risky, but generally, cutting into any tube is not a good idea). "The process is delicate, like handling food," she says. "Caution must be taken not to introduce microbes, since a large contamination may overwhelm the preservative system at some point and allow harmful bacteria or molds to grow in the product. Once the tube is cut open, the safeguards have been removed and the manufacturer can no longer guarantee the product."

These tubed products are also made with a different consumer handling expectations. "Manufacturers don't expect consumers to dip their fingers into these tubes [as] they would do in a jar,” explains cosmetic chemist Ginger King. “When [people do end up sticking their fingers into a tube], they can introduce germs in the product." King notes that opening the tube weakens the product’s already-weak preservation system. This can cause your product to grow mold, which can lead to serious infections.