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Spring is here—and the change in season may have you switching up your skincare routine. But if you're digging out last year's lightweight moisturizer, check the expiration date. Most opened products lose their effectiveness after one year and some even sooner, according to cosmetic chemist Ni'Kita Wilson. Expired products may not only lack potency, but could also cause an adverse skin reaction. If you're unsure how old something is, the general rule is to toss anything that has significantly changed in color or odor, or separated, clumped, thickened or thinned, says cosmetic chemist Mort Westman. All are signs that the product has gone bad. To be completely sure it's time to let go, here's a complete list of how long to keep your skincare products.

Moisturizer

Unopened: Two to three years

Opened: Up to one year