Many of us gals have been the victim of expired cosmetics. Here's the scenario. After seeing pics of that smokin' gloss we used to wear in high school, we rush to our beauty closet only to open the tube to a rank stank that we don't understand. Most beauty products do not have any smell, or if they do, it is very faint. If you start noticing some product BO, it's because that favorite gloss is dying a slow, bacteria-invested death in that dark, tightly sealed tube. Once the product has peaked, it can cause some pretty gross irritations or infections if used. To avoid all of the above, follow these general toss time guidelines.

Foundation: Six months for liquids and two years for powders
Bacteria like moisture. So after continuously sticking your grubby paws into a liquid foundation, the bacteria population skyrockets. Powders last longer because they aren't moist, however, many of the plant based ingredients will begin to crumble and become harder to blend after so long.

Mascara: Three months
Think about it this way; your mascara tube is a dark, wet place, just like any other place bacteria flourish. Although tubes have preservatives, they can only last so long once bacteria colonies have begun to takeover. After three months, you risk eye infection and are probably using a formula that just isn't working anymore.

Eyeliners and Shadows: Liquid liners for three months, cream eye shadows for six months, and pencil liners and shadows for two years
Liquid liners have the same song and dance as the mascara tube. Cream shadows can last a few months longer but are still subjected to moisture loving bacteria after so long. Powders are great because they lack that wetness factor that calls for continual replacement. Pencils are even better because you can sharpen them with each use and whisk away any bacteria easily.

Lipstick, gloss and liner: All last about two years
Lipstick has two arch enemies; bacteria and evaporation. As we've already crammed into your head, bacteria loves moisture, yada yada. But older lipsticks, especially long lasting or uber creamy formulas, have ingredients that evaporate over time. Once that happens the creamy factor is gone, baby, gone. Pencil liners may last a bit over two years because they can be sharpened on a regular basis.