Important Question: When Will Unopened Beauty Products Expire?

There's a good chance you used expired mascara this morning.

Unfortunately, we're not always able to get through our favorite products, especially when switching them up with the latest formulas and trends (hello, colorblocking!), before their times run out. That's of course figuratively speaking because you could have a tube that's half full and seemingly still intact, yet ridden with bacteria. Eek!

We've done the dirty work when it comes to breaking down when exactly you should toss what after using. Some brands are also helping to take the mystery out of the equation by including special expiration logos right on their packaging.

But what about those times you find yourself with a surplus after being gifted or going a little overboard on those sales (yes, it is possible) and plan to save your products for a rainy day? If a product is sealed, does it abide by the same guidelines as when it is opened, or is it frozen in time, just as fresh as the day you bought it 10 years later?

According to Stephanie Koutikas, makeup artist and Creative Director at Mehron Makeup, it isn't always so cut and dry. "You'll want to take into consideration whether the product contains skin actives (the potency of the active can diminish over time depending on how reactive it is), preservation (natural preservatives may have a shorter shelf life, whereas synthetics can lead to longer expiration dates), and storage (the environment of the store that is selling the product or at your home can affect the integrity of the product. So you'll want to make sure it's kept at a cool temp away from sunlight)," she explained.

"Before our hair products can be put on the market, they go through a stability testing process," added Lisa Silliker, Director of Management at Pai-Shau (she's in charge of researching, developing, sourcing, and positioning all of the brand's products and packaging). "Product is put through various tests of temperature and light exposure. These tests will determine changes that will take place over the course of a period of time. Elevating the temperature for a few weeks will determine the changes and growth of bacteria that will take place after several months or years at room temperature. The government has guidelines and limits for how much bacteria is safe and acceptable. This dictates time after opening or expiration dates."

The container can also be a factor. "If the product comes in an airless pump, it will last much longer than if it comes in a jar that consumers will typically put their hands into," Silliker noted.

That said, there are still some general guidelines experts have come to live by. From eye cream (it's more sensitive than you might think!) to lip gloss (you may be able to hold on to that a bit), read on as they share some of their personal rules of thumb, along with some additional tips for ensuring you don't end up with spoiled moisturizer on your hands . . . literally.