Plenty of us have done it: You find a skincare product you love and immediately want to buy it in bulk to save money–and so you won’t run out. But just because you can do that doesn’t mean you should. Sure, you could cash in on multiple two-for-one deals at once, but some skincare products have shorter expiration dates–which means buying in bulk could actually end up costing you more if you end up tossing half of what you bought in a couple months.

“Two or three at a time should be fine for most skincare products,” says Peterson Pierre, MD, a board-certified dermatologist in Los Angeles. “If it’s a dozen, I would caution against it because ingredients do expire and you want to ensure maximum freshness and potency.”

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