Mascara has a shelf life of between three and six months. Any longer than this and you are potentially plastering your lashes with a bacteria laden wand which can cause infection. If you can’t remember when you bought it, bin it!
Foundation should be kept for no longer than a year as a stale base can cause breakouts. To protect against bacteria and outside dirt, go for a foundation with a pump-based lid -- it is safer than a screw top, which lets more air into the product.
If you are a girl who loves her lipsticks and has more colours than you can count, this could be bad news. You are only meant to use the same lipstick for up to two years. After that it should be thrown away regardless of how often you used it. Saving that expensive lipstick for special occasions could cause bacteria to build and then when you apply it to your lips, you feed infection directly your mouth.
Like mascara, eyeliner can become infected with bacteria, especially liquid liners. Eye pencils can last a little longer because the sharpening keeps it fresh, but be warned -- as soon as you lose the lid or leave the end uncovered, the liner should head for the bin. Imagine all the dirt that is picked up from being left exposed – do you really want that in your eye?