It raises the question: Does lotion ever, uh, go bad? And if so, when? Read on for all the details. However, expiration dates can differ depending on the product, so be sure to check the label each time. For instance, lightweight hydrators tend to be water-based to achieve a thinner consistency—and as you may know, water creates a fertile breeding ground for bacteria. While most market products do include safe preservatives to make the formula shelf-stable, they still typically have a shorter lifespan. As for oil-based lotions (read: thick, buttery confections)? Those tend to last a bit longer, as there’s no water to make it vulnerable to bacteria. Of course, user behavior might introduce water into the formula (which we’ll get into later), so you’ll still want to be mindful of any signs of wear. As Jana Blankenship, product formulator and founder of the natural beauty brand Captain Blankenship, tells us about creating your own lotion, keep water-based confections (with aloe, rosewater, and the like) for up to one month. Because DIY formulations don’t have preservatives, they don’t last too long before becoming rancid—or worse, contaminated. For liquid-free lotions (with shea butter, moringa butter, et al.), the lotion should keep for up to one year. Just remember to scoop it out with clean, dry fingers or a clean spoon, Blankenship warns, lest you introduce bacteria into the formula. That said, if you notice any of these signs before the expiration date, your lotion may have gone rancid: That’s why experts recommend storing your bottles in a cool, dry area—like your bedroom. Perhaps place it outside the bathroom door while you’re showering if you want to apply immediately after toweling off. You can use a clean spoon or beauty spatula to scoop out the lotion each time—just make sure these are clean and dry as well. While we admire your loyalty to the coveted lotion, you’ll still want to part ways, for a couple of reasons: First, a spoiled product has the potential to cause skin reactions or breakouts for some—even if you don’t notice any signs of wear, you don’t want to run the risk. Second, it simply may not work as well, especially if there are active ingredients (like antioxidants, hyaluronic acid, and ceramides) involved. As board-certified dermatologist Steven Wang, M.D., co-founder of Dr. Wang Herbal Skincare, once told us, shelf life works in two ways. There’s the rancidity point, but “you can even go further and think about the functional shelf life of active ingredients.” Translation: Even if a lotion past its prime doesn’t look rancid or spark irritation, its active ingredients may lose their power over time—and in that case, it’s not doing much for your skin.