Why do you want to be diligent about cleaning makeup, just as you may be about cleaning brushes? Simple: “When you don’t sanitize your makeup regularly, bacteria will grow on it. Bacteria can cause irritation and acne when it comes into contact with your face,” says Titus Tse, co-founder of Coral UV. In the same way we are warned against swapping other personal items, we need to keep the same mentality for makeup. Sure, makeup is fun and therefore gives the air of it being swappable: But sharing makeup should always be a no-go. Removing it from the bathroom may also help you avoid mold. “If you have a small bathroom that gets very steamy, move your makeup, brushes, and sponges to a clean, dry place where they’re less likely to go through the humidity cycle and get moldy,” says Patinkin. Derms agree, too: “Your natural oils, bacteria, makeup, dead skin cells, dirt, and grime accumulate on the brush, and then you are just reapplying that on a daily basis,” says holistic board-certified dermatologist Keira Barr, M.D. “This can lead to a lot of skin issues—acne, contact dermatitis, infections—but then from a functional aspect the brushes aren’t going to work.” For a full explainer on how to clean your brushes (and how often) check out our brush cleaning guide. As a general rule, always avoid dipping fingers or used brushes into jars, as this will transfer bacteria into the pot where it can grow and fester. “With liquid makeup or mascara, you can add a small amount of rubbing alcohol directly into the container or onto your applicator, but be careful—if you use too much, it can change the texture of the product or irritate your skin or eyes,” she says. So start with a very small amount (a single drop), and whisk it in. You can always add more if you feel the size of the jar warrants it, but you can never remove it if you feel you’ve gone too far. Or she has another tip for application: “If you’re worried about something like foundation being contaminated, put it on the back of your (clean) hand, very lightly spray with rubbing alcohol and let it dry, then apply as usual.” Don’t worry, you don’t have to every time you’re applying foundation—especially if you are just using your own bottle and you have no fear that it’s been contaminated—only if you have doubts and need to take extra precautions. “It’s important to note that the light must be touching it—for example, you wouldn’t want to bunch something up and throw it in there, as the folds will not allow light to reach some places,” says Tse. “If you place a foundation sponge in the box, you can ensure 99.9% sanitation by either placing it in the hanging basket, which ensures it gets hit by the light at all angles or running it through two cycles and turning it over.” The first thing to look for is the actual expiration date, which should be listed on the label as a number inside or beside a jar. Other signs that something is past its prime is if the color is off or separating (like in the case of pigmented liquids). You can also look for textural or consistency changes. Finally, be very mindful of changes of smell in all liquid- or water-based products: “Use the smell test to make sure mascaras and liquids don’t have a bitter odor,” says Patinkin.